diff --git a/mmdet3d/core/visualizer/open3d_vis.py b/mmdet3d/core/visualizer/open3d_vis.py
index 08d1d31534..d0fc8a1a66 100644
--- a/mmdet3d/core/visualizer/open3d_vis.py
+++ b/mmdet3d/core/visualizer/open3d_vis.py
@@ -1,9 +1,14 @@
 import cv2
 import numpy as np
-import open3d as o3d
 import torch
 from matplotlib import pyplot as plt
-from open3d import geometry
+
+try:
+    import open3d as o3d
+    from open3d import geometry
+except ImportError:
+    raise ImportError(
+        'Please run "pip install open3d" to install open3d first.')
 
 
 def _draw_points(points,
diff --git a/mmdet3d/core/visualizer/show_result.py b/mmdet3d/core/visualizer/show_result.py
index 2b5f059198..522604ad79 100644
--- a/mmdet3d/core/visualizer/show_result.py
+++ b/mmdet3d/core/visualizer/show_result.py
@@ -3,8 +3,6 @@
 import trimesh
 from os import path as osp
 
-from .open3d_vis import Visualizer
-
 
 def _write_ply(points, out_filename):
     """Write points into ``ply`` format for meshlab visualization.
@@ -81,6 +79,8 @@ def show_result(points, gt_bboxes, pred_bboxes, out_dir, filename, show=True):
         filename (str): Filename of the current frame.
         show (bool): Visualize the results online.
     """
+    from .open3d_vis import Visualizer
+
     if show:
         vis = Visualizer(points)
         if pred_bboxes is not None:
diff --git a/requirements/optional.txt b/requirements/optional.txt
index a9b8ad8e25..d3434d5046 100644
--- a/requirements/optional.txt
+++ b/requirements/optional.txt
@@ -1 +1,2 @@
+open3d
 waymo-open-dataset-tf-2-1-0==1.2.0
diff --git a/requirements/tests.txt b/requirements/tests.txt
index 1297a5a2da..303cc37d6f 100644
--- a/requirements/tests.txt
+++ b/requirements/tests.txt
@@ -5,7 +5,6 @@ interrogate
 isort
 # Note: used for kwarray.group_items, this may be ported to mmcv in the future.
 kwarray
-open3d
 pytest
 pytest-cov
 pytest-runner
diff --git a/setup.cfg b/setup.cfg
index 5fd1a7aae9..b4c6c44fee 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -8,6 +8,6 @@ line_length = 79
 multi_line_output = 0
 known_standard_library = setuptools
 known_first_party = mmdet,mmdet3d
-known_third_party = cv2,load_scannet_data,lyft_dataset_sdk,m2r,matplotlib,mmcv,nuimages,numba,numpy,nuscenes,open3d,pandas,plyfile,pycocotools,pyquaternion,pytest,recommonmark,scannet_utils,scipy,seaborn,shapely,skimage,tensorflow,terminaltables,torch,trimesh,waymo_open_dataset
+known_third_party = cv2,load_scannet_data,lyft_dataset_sdk,m2r,matplotlib,mmcv,nuimages,numba,numpy,nuscenes,pandas,plyfile,pycocotools,pyquaternion,pytest,recommonmark,scannet_utils,scipy,seaborn,shapely,skimage,tensorflow,terminaltables,torch,trimesh,waymo_open_dataset
 no_lines_before = STDLIB,LOCALFOLDER
 default_section = THIRDPARTY