Abstract: In order to investigate the effect of reburning chamber structure on the performance of solid rocket ejector engine in flight, kerosene was injected in the form of droplets with a diameter of 0.01 mm at a speed of 80 m/s and an injection mass flow rate of 0.2 kg/s under the operative condition of engine flight Mach 0.6. Kerosene and air adopt one-step reaction, and the combustion flow numerical calculations of the built-in expansion and built-in contraction structures are carried out, respectively. The injection efficiency, thrust, thrust gain and combustion efficiency are compared. It is obtained that the injection performance of the expansion structure engine is better, but the combustion efficiency and thrust gain of the contraction structure engine are much greater than that of the expansion structure engine. Based on the built-in contraction structure, the effects of different angles between kerosene injection direction and combustion chamber axis (90° to 180°) on engine performance are studied. The results show that it is difficult to achieve combustion when kerosene injection angle is less than 130°, under the cases of being able to burn, the engine performance parameters are basically the same, and the thrust and thrust gain increase slightly with the increase of injection angle.