可行方案：

E:\pyth\Anaconda\envs>python -m pip debug --verbose
WARNING: This command is only meant for debugging. Do not use this with automation for parsing and getting these details, since the output and options of this command may change without notice.
pip version: pip 21.0.1 from E:\pyth\Anaconda\lib\site-packages\pip (python 3.8)
sys.version: 3.8.5 (default, Sep 3 2020, 21:29:08) [MSC v.1916 64 bit (AMD64)]
sys.executable: E:\pyth\Anaconda\python.exe
sys.getdefaultencoding: utf-8
sys.getfilesystemencoding: utf-8
locale.getpreferredencoding: cp936
sys.platform: win32
sys.implementation:
name: cpython
'cert' config value: Not specified
REQUESTS_CA_BUNDLE: None
CURL_CA_BUNDLE: None
pip._vendor.certifi.where(): E:\pyth\Anaconda\lib\site-packages\pip\_vendor\certifi\cacert.pem
pip._vendor.DEBUNDLED: False
vendored library versions:
appdirs==1.4.4
CacheControl==0.12.6
colorama==0.4.4
contextlib2==0.6.0.post1 (Unable to locate actual module version, using vendor.txt specified version)
distlib==0.3.1
distro==1.5.0 (Unable to locate actual module version, using vendor.txt specified version)
html5lib==1.1
msgpack==1.0.2 (Unable to locate actual module version, using vendor.txt specified version)
packaging==20.9
pep517==0.9.1
progress==1.5
pyparsing==2.4.7
requests==2.25.1
certifi==2020.12.05
chardet==4.0.0
idna==2.10
urllib3==1.26.2
resolvelib==0.5.4
retrying==1.3.3 (Unable to locate actual module version, using vendor.txt specified version)
setuptools==44.0.0 (Unable to locate actual module version, using vendor.txt specified version)
six==1.15.0
toml==0.10.2
webencodings==0.5.1 (Unable to locate actual module version, using vendor.txt specified version)
Compatible tags: 30
cp38-cp38-win_amd64
cp38-abi3-win_amd64
cp38-none-win_amd64
cp37-abi3-win_amd64
cp36-abi3-win_amd64
cp35-abi3-win_amd64
cp34-abi3-win_amd64
cp33-abi3-win_amd64
cp32-abi3-win_amd64
py38-none-win_amd64
py3-none-win_amd64
py37-none-win_amd64
py36-none-win_amd64
py35-none-win_amd64
py34-none-win_amd64
py33-none-win_amd64
py32-none-win_amd64
py31-none-win_amd64
py30-none-win_amd64
cp38-none-any
py38-none-any
py3-none-any
py37-none-any
py36-none-any
py35-none-any
py34-none-any
py33-none-any
py32-none-any
py31-none-any
py30-none-any

查看openCV的版本：

E:\pyth\Anaconda\envs>python
Python 3.8.5 (default, Sep 3 2020, 21:29:08) [MSC v.1916 64 bit (AMD64)] :: Anaconda, Inc. on win32

Warning:
This Python interpreter is in a conda environment, but the environment has
not been activated. Libraries may fail to load. To activate this environment
please see https://conda.io/activation

Type "help", "copyright", "credits" or "license" for more information.
>>> import cv2
>>> cv2.__version__
'4.5.1'

下载地址：https://mirrors.tuna.tsinghua.edu.cn/pypi/web/simple/opencv-python/

E:\pyth\Anaconda\Scripts>pip install --user opencv_python-4.5.1.48-cp38-cp38-win_amd64.whl
Processing e:\pyth\anaconda\scripts\opencv_python-4.5.1.48-cp38-cp38-win_amd64.whl
Requirement already satisfied: numpy>=1.17.3 in e:\pyth\anaconda\lib\site-packages (from opencv-python==4.5.1.48) (1.19.2)
Installing collected packages: opencv-python
Successfully installed opencv-python-4.5.1.48

参考文章：https://blog.csdn.net/qq_40207793/article/details/104659789