Abstract: Hot tests were conducted and experimental data was analyzed in order to select an optimal structure for gas generator.The combustion performance was analyzed and the size of injectors,the characteristic chamber length and the geometric characteristic of combustor was examined.The results suggest that:In a certain extant enlarging the size of injectors does not affect the combustion efficiency,at the same time the ignition delay is shorten and the boundary of adjustment of mass flow rate is expanded;Increase of characteristic chamber length benefits combustion efficiency;Geometric characteristic of combustor also has a great impact on combustion efficiency.The flame segment of converge-diverge shape influences the combustion process,and then decreases the combustion efficiency.The combustor with converge-diverge shape is not recommended during the design of gas generator.