A base station system and method for call setting up, handing over and releasing in hybrid network are disclosed. The base station system consists of BSC, TC, several BTSs and a band-width guaranteed IP network. IP mode transport and traditional TDM mode transport between BSC and TC are simultaneity supported in the system, and BTS supports TDM mode or IP mode. The invention provides: compatibility with TDM, which protects the providers' investment; smooth transition from TOM to IP, which decreases investing risk; flexible choice for different physical layer or data link layer transmission apparatuses to bear IP message, which facilitates the providers to constitute their networks. In IP mode, data service can share bandwidth with the mute frames of voice service, the system can coexist with different IP networks, and the control user planes are independent so as to simplify the developing procedure and reduce the maintaining cost.