Abstract: With the miniaturization of RF products, especially the gradual application of RF SIP products. There are more and more applications of RF integrated products such as multilayer PCB substrate RF components. The research of RF signal transmission performance in the substrate is also becoming more and more important. In this paper, the RF performance of the substrate based on the multilayer PCB is simulated and tested. The transmission performance of the RF substrate in the DC-40GHz range has been verified. At the same time, for the extremely important transmission loss in the RF transmission performance, the optimization of the RF transmission loss is achieved by improved medium thickness or copper foil material, the transmission loss is reduced by more than 20%. According to the space application environment, through deep charge and discharge, total dose test, it is shown that the multilayer PCB substrate can meet the space application.