Abstract: Combining the gas thermodynamics with the isobaric ejector design theory, the calculation method of thermodynamic parameters of high temperature gas is presented, and the ejector design scheme based on the high temperature gas ejection is proposed. Through the docking experiment between the ejector and the gas generator, the working performance of zero injection and secondary flow are studied, and the influence of temperature change of ejected gas flow on the working performance are also studied. The experimental results show that the total inlet pressure can reach 3.89 kPa with the secondary flow at 360 g/s, and the variation of the ejector gas temperature within 100 K below the design point has no effect on the ejector performance, which verifies the reliability of performance calculation analysis and engineering design method of the supersonic ejector based on high temperature gas injection, and the relevant research results provide guidance suggestions for parameter optimization of the gas generator.