Abstract: Based on the phenomenon of single-side local high temperature of throat and high jump of weld temperature during steady-state test ignition of the engine. which seriously endangers the reliability of the engine, CFD simulation was used to model the structure of the head injector and optimize the distribution structure in the flow channel combined with the flow resistance mathematical model. To achieve the reduction of jet flow resistance and improve the non-uniformity of flow caused by impact, and optimize the combustion structure and liquid film cooling scheme in the side zone by adjusting the impact parameters, optimize the mixing ratio in the side zone, and reduce the throat temperature and circumferential temperature difference. The improved engine has been verified by experiments. Under the condition of unchanged performance, the temperature of the high-altitude simulated thermal test throat was reduced from nearly 1 500 ℃ to 1 270 ℃, the temperature at the headbody weld was reduced from 520 ℃ to 310 ℃, and the temperature difference of the engine body was controlled within 50 ℃, which effectively solved the problem of high temperature in the engine throat. The service life and reliability of the engine were improved.