If you use various pip install, conda install, and add similar -f https://pytorch-geometric.com/whl/torch-1.8.0+cu102.html, -f https://data.pyg.org/ Whl/torch-1.8.0+cu102.html and other suffix links, and then try various combinations of torch-geometric and torch-scatter torch-sparse torch-cluster, torch-spline-conv after the installation of different versions still does not succeed, you might as well Try the following methods, you may be surprised!
Official website address:
Find the version corresponding to the torch you installed, such as torch1.8.1 and cu102, click to enter
https://pytorch-geometric.com/whl/
After entering, you will see the following page:
Just find the whl file corresponding to the python version and operating system version, such as python3.8 in the windows system, download the corresponding cp38-win type whl respectively, download it to the local folder, and pass Switch the path to the corresponding folder 1 on the command line and use pip install (full package name).whl (full package name).whl (full package name).whl (full package name). whl can decompress and install the whl files corresponding to the four local packages, and then install torch-geometric.
If there are still errors when running the corresponding program, downgrade the torch-geometric version, because the default installation may directly install according to the latest version (2.4.0), which can be downgraded to 2.1 or 2.0. 
The following is my smooth and compatible installation version reference:
