In view of the ejector optimization problem considering the comprehensive influence of multiple factors, based on the ejector function method, the mathematical characteristics of static pressure matching function were studied and the singular points on the mathematical curve were analyzed. On this basis, the multi branch characteristic curves were obtained by programming and benchmark progression induction method, and the characteristics of solutions under different branches were analyzed. In addition, the influences of mixing chamber back pressure, total pressure ratio of primary and secondary flow and mixing nonuniformity on the ejector performance were studied, and the design concepts of static pressure characteristic curve and critical curve were proposed. The reliability of the ejector function method was verified by comparing with the experimental data. The results showed that the design performance of the ejector was better when it was close to the critical curve. The mixing nonuniformity had a great influence on the ejector performance, when the nonuniformity was 1.5, compared with the ideal state, the maximum error of the ejecting coefficient reached 32.73%. When considering the wall friction design, the friction coefficient formula model should be modified. The results provide an important guidance for the optimal design of ejector.