When I compile this part of the code（ ic/rs at master · dfinity/ic · GitHub ）, how to start a local network
Are you trying to contribute to the IC repo? If you are just trying to run it for development, we recommend use DFX, which bundles a local replica for you and provides additional tooling.
sh -ci "$(curl -fsSL https://smartcontracts.org/install.sh)"
Yes, I use dfx for development, but I prefer to know the details of IC work