I used photon in unity.
But now my project is a bp project, so i cant use photon.
Therefore, is there any network framework for blueprint?
Shortly no. There is blueprint nodes as “IsLoggedIn”, “StartSession”, etc. But to use them you must setup and configure an OnlineSubsystem. Here is documentation article: Online Subsystem | Unreal Engine Documentation
In case you are going to use Steam; Online Subsystem Steam | Unreal Engine Documentation