Abstract: The mathematical model of a low-thrust power system with high combustor pressure is set up.The numerical computation for this system and analysis of the influence of combustion time delay on this system have been carried out with the characteristic method and the fourth-order Runge-Kutta method.The computed results show that the response of the power system becomes slower,the overshoot of engine performance parameter becomes greater and the time required for reaching the steady state becomes longer,if the combustion time delay is greater.When orbit control and attitude control rocket engines share the same propellant feed system,thus attitude-control rocket engine is affected more greatly by the combustion time delay.Finally,some methods are proposed to decrease the combustion time delay.The conclusions drawn in this paper provide the basis for improving its response characteristics.