This paper introduces an X-band multi-channel up and down conversion system with variable bandwidth. The transceiver can splice bandwidth, closed-loop self-test mode and other functions. It has channel bandwidth switching mode, pulse modulation mode and phase noise lower than - 104dbm/ Hz@1KHz And other excellent properties. The master-slave mode is completed by switching. The system includes high-speed frequency synthesizer module, power module, circulator, etc. Connected with the external test ant port, it is used for X-band transceiver signal test, provides frequency agility mode, and can effectively test the intermediary system.