Satellite wave-absorbing material was the core component that met the isolation requirement in the high-power use of antennas and microwave components under complex space environmental conditions. In this paper， the relationship between the vacuum power tolerance of satellite wave-absorbing materials and the key elements of the raw material preparation process was studied.Firstly，the electromagnetic wave absorption mechanism of satellite wave-absorbing materials was introduced.The electromagnetic parameters of satellite wave-absorbing materials were directly related to the excellent electromagnetic wave absorption performance.Secondly，the key factors of raw material preparation which affect the stability of electromagnetic parameters and the machining characteristics of molding materials were given. Then， a set of verification platform for the power tolerance of satellite wave-absorbing materials was constructed to carry out power tests. Waveguide absorption load test pieces were made respectively for the raw materials prepared by two curing methods. The results show that：（1）The uncured small molecules remaining in the wave-absorbing material without high temperature pretreatment lead to the precipitation increase of coagulable volatiles under the condition of high temperature and vacuum， and the oxidation reaction occur with the silver plating layer of the outer conductor， so that the VSWR change rate of the load component is larger.（2）After high temperature pretreatment， the vacuum mass loss and coagulable volatiles of the wave-absorbing materials at high temperature are effectively controlled， and their electromagnetic parameters tend to be stable. There is little difference in the VSWR change rate of the load components before and after the test. Therefore， high temperature pretreatment is the key factor in the process of raw material preparation. The effective implementation of this curing method is helpful to the application of satellite wave-absorbing materials and improve the reliability and safety of spacecraft in orbit service.