Abstract: Iteration method with stationary point was put forward for making working process simulation of internal combustion pump more actual, comprehensive and embedded, in which, the required working condition rotational speed was the stationary point. Through iteration of the torque to crankshaft end according to the difference between required and simulating rotational speed, internal combustion pump (ICP) will converge at the required condition. Based on the computer aided design (CAD) software of Solid works and computer aided engineering (CAE) software of Adams, the virtual prototype of three-cylinder, ICP was constructed, then the principle, flow chart and application of iteration method with stationary point were described. Under calibrated working condition, the simulation of ICP can converge through 13 working cycles, and the running stability reaches 3.62% which can fullfill the application; the computational accuracy of angular speed of crankshaft is improved by 2.13% than traditional method.