Abstract: In order to improve multilevel isotonic mixed ejector's performance, all kind parameters of multilevel isotonic mixed ejector's were matched and optimized. Perfect ejector compress ratio and efficiency were acquired. This paper analyzes the one level isotonic mixed ejector by experiment, indicated the effects of one level isotonic mixed ejector's parameters change, and then, make certain the multilevel isotonic mixed ejector's level principle, match and optimize multilevel isotonic mixed ejector's all kinds of parameters. As a result, if the ejecting Mach number,the ejected temperature, one level isotonic mixed ejector's ejecting coefficient and compress ratio are matched and optimized, multilevel isotonic mixed ejector's performance will be improved evidently.