diff --git a/change/office-ui-fabric-react-2019-08-19-17-03-13-sohuts-use-getdocument-in-focuszone.json b/change/office-ui-fabric-react-2019-08-19-17-03-13-sohuts-use-getdocument-in-focuszone.json
new file mode 100644
index 0000000000000..12692faf88042
--- /dev/null
+++ b/change/office-ui-fabric-react-2019-08-19-17-03-13-sohuts-use-getdocument-in-focuszone.json
@@ -0,0 +1,8 @@
+{
+  "type": "patch",
+  "comment": "Use getDocument instead document in FocusZone and FocusTrapZone",
+  "packageName": "office-ui-fabric-react",
+  "email": "sohuts@microsoft.com",
+  "commit": "c4766bf28c3c6fe6021e2a0f277524bcc64064b4",
+  "date": "2019-08-19T15:03:13.879Z"
+}
diff --git a/packages/office-ui-fabric-react/src/components/FocusTrapZone/FocusTrapZone.tsx b/packages/office-ui-fabric-react/src/components/FocusTrapZone/FocusTrapZone.tsx
index 4c553eba905f3..455eb07f64e36 100644
--- a/packages/office-ui-fabric-react/src/components/FocusTrapZone/FocusTrapZone.tsx
+++ b/packages/office-ui-fabric-react/src/components/FocusTrapZone/FocusTrapZone.tsx
@@ -6,6 +6,7 @@ import {
   getFirstTabbable,
   getLastTabbable,
   getNextElement,
+  getDocument,
   focusAsync,
   initializeComponentRef,
   on
@@ -67,7 +68,7 @@ export class FocusTrapZone extends React.Component<IFocusTrapZoneProps, {}> impl
     if (
       !this.props.disabled ||
       this.props.forceFocusInsideTrap ||
-      !elementContains(this._root.current, document.activeElement as HTMLElement)
+      !elementContains(this._root.current, this._getDocument().activeElement as HTMLElement)
     ) {
       this._returnFocusToInitiator();
     }
@@ -162,7 +163,7 @@ export class FocusTrapZone extends React.Component<IFocusTrapZoneProps, {}> impl
       // even when it's not. Using document.activeElement is another way
       // for us to be able to get what the relatedTarget without relying
       // on the event
-      relatedTarget = document.activeElement as Element;
+      relatedTarget = this._getDocument().activeElement as Element;
     }
 
     if (!elementContains(this._root.current, relatedTarget as HTMLElement)) {
@@ -213,7 +214,7 @@ export class FocusTrapZone extends React.Component<IFocusTrapZoneProps, {}> impl
 
     this._previouslyFocusedElementOutsideTrapZone = elementToFocusOnDismiss
       ? elementToFocusOnDismiss
-      : (document.activeElement as HTMLElement);
+      : (this._getDocument().activeElement as HTMLElement);
     if (!disableFirstFocus && !elementContains(this._root.current, this._previouslyFocusedElementOutsideTrapZone)) {
       this.focus();
     }
@@ -226,12 +227,13 @@ export class FocusTrapZone extends React.Component<IFocusTrapZoneProps, {}> impl
       return this !== value;
     });
 
-    const activeElement = document.activeElement as HTMLElement;
+    const doc = this._getDocument();
+    const activeElement = doc.activeElement as HTMLElement;
     if (
       !ignoreExternalFocusing &&
       this._previouslyFocusedElementOutsideTrapZone &&
       typeof this._previouslyFocusedElementOutsideTrapZone.focus === 'function' &&
-      (elementContains(this._root.current, activeElement) || activeElement === document.body)
+      (elementContains(this._root.current, activeElement) || activeElement === doc.body)
     ) {
       this._focusAsync(this._previouslyFocusedElementOutsideTrapZone);
     }
@@ -277,7 +279,7 @@ export class FocusTrapZone extends React.Component<IFocusTrapZoneProps, {}> impl
     }
 
     if (FocusTrapZone._focusStack.length && this === FocusTrapZone._focusStack[FocusTrapZone._focusStack.length - 1]) {
-      const focusedElement = document.activeElement as HTMLElement;
+      const focusedElement = this._getDocument().activeElement as HTMLElement;
 
       if (!elementContains(this._root.current, focusedElement)) {
         this.focus();
@@ -304,4 +306,8 @@ export class FocusTrapZone extends React.Component<IFocusTrapZoneProps, {}> impl
       }
     }
   };
+
+  private _getDocument(): Document {
+    return getDocument(this._root.current)!;
+  }
 }
diff --git a/packages/office-ui-fabric-react/src/components/FocusZone/FocusZone.tsx b/packages/office-ui-fabric-react/src/components/FocusZone/FocusZone.tsx
index c2099689c9e4a..c507303b816b7 100644
--- a/packages/office-ui-fabric-react/src/components/FocusZone/FocusZone.tsx
+++ b/packages/office-ui-fabric-react/src/components/FocusZone/FocusZone.tsx
@@ -139,7 +139,7 @@ export class FocusZone extends React.Component<IFocusZoneProps> implements IFocu
 
       let parentElement = getParent(root, ALLOW_VIRTUAL_ELEMENTS);
 
-      while (parentElement && parentElement !== document.body && parentElement.nodeType === 1) {
+      while (parentElement && parentElement !== this._getDocument().body && parentElement.nodeType === 1) {
         if (isElementFocusZone(parentElement)) {
           this._isInnerZone = true;
           break;
@@ -160,7 +160,7 @@ export class FocusZone extends React.Component<IFocusZoneProps> implements IFocu
       this._updateTabIndexes();
 
       if (this.props.defaultActiveElement) {
-        this._activeElement = getDocument()!.querySelector(this.props.defaultActiveElement) as HTMLElement;
+        this._activeElement = this._getDocument().querySelector(this.props.defaultActiveElement) as HTMLElement;
         this.focus();
       }
     }
@@ -168,7 +168,7 @@ export class FocusZone extends React.Component<IFocusZoneProps> implements IFocu
 
   public componentDidUpdate(): void {
     const { current: root } = this._root;
-    const doc = getDocument(root);
+    const doc = this._getDocument();
 
     if (doc && this._lastIndexPath && (doc.activeElement === doc.body || doc.activeElement === root)) {
       // The element has been removed after the render, attempt to restore focus.
@@ -309,16 +309,15 @@ export class FocusZone extends React.Component<IFocusZoneProps> implements IFocu
 
   private _evaluateFocusBeforeRender(): void {
     const { current: root } = this._root;
-    const doc = getDocument(root);
 
+    const doc = this._getDocument();
     if (doc) {
       const focusedElement = doc.activeElement as HTMLElement;
 
       // Only update the index path if we are not parked on the root.
       if (focusedElement !== root) {
         const shouldRestoreFocus = elementContains(root, focusedElement, false);
-
-        this._lastIndexPath = shouldRestoreFocus ? getElementIndexPath(root as HTMLElement, doc.activeElement as HTMLElement) : undefined;
+        this._lastIndexPath = shouldRestoreFocus ? getElementIndexPath(root as HTMLElement, focusedElement) : undefined;
       }
     }
   }
@@ -500,7 +499,7 @@ export class FocusZone extends React.Component<IFocusZoneProps> implements IFocu
       return;
     }
 
-    if (document.activeElement === this._root.current && this._isInnerZone) {
+    if (this._getDocument().activeElement === this._root.current && this._isInnerZone) {
       // If this element has focus, it is being controlled by a parent.
       // Ignore the keystroke.
       return;
@@ -948,7 +947,7 @@ export class FocusZone extends React.Component<IFocusZoneProps> implements IFocu
   private _getOwnerZone(element?: HTMLElement): HTMLElement | null {
     let parentElement = getParent(element as HTMLElement, ALLOW_VIRTUAL_ELEMENTS);
 
-    while (parentElement && parentElement !== this._root.current && parentElement !== document.body) {
+    while (parentElement && parentElement !== this._root.current && parentElement !== this._getDocument().body) {
       if (isElementFocusZone(parentElement)) {
         return parentElement;
       }
@@ -1060,4 +1059,8 @@ export class FocusZone extends React.Component<IFocusZoneProps> implements IFocu
   private _portalContainsElement(element: HTMLElement): boolean {
     return element && !!this._root.current && portalContainsElement(element, this._root.current);
   }
+
+  private _getDocument(): Document {
+    return getDocument(this._root.current)!;
+  }
 }