Abstract: When hypersonic spacecraft reenters the space atmosphere, the dense plasma sheath will be formed on the surface of hypersonic spacecraft due to shock wave heating and ablation of thermochemical protective materials. The formation of sheath will cause the interruption of radio communication signals so that the reduction and elimination of black barriers are essential for telemetry equipment communication and national defense security. It is necessary to know the information on plasma electron density parameters in the black barrier and then could reduce and eliminate the black barrier. In order to solve this problem, the first, a novel composite probe was proposed by us, which can diagnose the electron density parameters in the high-temperature flow field plasma in real-time and effectively. At the same time, the data acquisition, comparison and model modification of the composite probe were completed in the ground simulated space plasma experimental equipment. The results were compared with other detection equipment, and the uncertainty was less than 17%. The two probe techniques work independently of each other, and complement each other and compare with each other. Secondly, the release test of electrophilic substances can effectively reduce the electron density parameter information and finally serve the national aerospace department. This paper will make a systematic review of the research work in this field.