Radar communication integration makes radar have communication function by sharing some subsystems of radar, usually sharing RF subsystem of radar. Transceiver module is one of the main components of RF front-end of phased array radar. It uses the transmit branch of radar T / R module to transmit communication waveform. The linear characteristic of transmit branch directly determines the feasibility of its application in communication. This paper describes the working principle of the radar communication integrated common module, focuses on the influence of the performance of the transmitting channel of the module on the communication waveform, analyzes the EVM index of the transmitting channel, and gives the EVM test results of the S-band transmitting module.