Abstract: Based on a type of Marine monitoring engineering background for spaceborne SAR, In this paper, the spaceborne SAR application characteristics and drawing requirements to the EMC design of cable network were expounded firstly. The connotation and the rules of design about cables-network applied to the spaceborne SAR were discussed then , Select the entire star cable net key-module-used in beam control cable components as an example, The EMC design process of which was introduced in detail. by setting up the circuit model about the drive,load and the cable module using the Ansoft、SIWAVE、Q3D softwares,the transmission characteristic of signal in the route was designed, finally the measure result proved the emulator and design were in effect.