Abstract: The pressure matching device can effectively utilize the exhaust steam of the steam turbine. It is an energy-saving and environment-friendly fluid machinery. Focus on the poor ejection performance of the pressure matcher with a large compression ratio of a subcritical unit,a three-dimensional model of the pressure matcher is carried out using the computational fluid dynamics(CFD)method. The effects of nozzle and mixing section parameters as well as variable geometry with adjusting cone on the ejection coefficient are studied. The results show that under a given working condition,there is an optimal parameter range for some structures of the nozzle and mixing section to maximize the ejection coefficient;there is an optimal position of the adjusting cone to further improve the ejection coefficient as well. The optimized structure increases the ejection coefficient from 0.13 to 0.23. The research results have important guiding significance for the structure optimization of the pressure matcher.