Abstract: A method, a communication system, and a device for obtaining a connection frame number (CFN) are provided to obtain the CFN under a situation of applying high speed package access (HSPA). The method includes the following steps. A downlink node synchronization request including radio network controller (RNC) time information is sent to a base station through a high-speed downlink shared channel (HS-DSCH) frame protocol (FP). An uplink node synchronization response including base station time information sent from the base station through the HS-DSCH FP is received. A CFN is obtained according to a preset RNC frame number (FN), a preset frame offset, the RNC time information, and the base station time information.