Abstract: Aiming at influence of wedge-cam mechanism on the starting character of radial six-cylinder internal combustion pump, the working principle was described, and the models of mechanical efficiency of wedge-cam mechanism and the resistance torque to crankshaft by springs were constructed. Simulation results showed that the efficiency was more than 97%, which was a incremetal parabolic curve versus the wedge angle. The resistance torque sum of all springs was a cosine wave with an amplitude of 4.43 N·m and cycle of 120°(CA), which resulted in a starting resistance torque of 4.43 N·m to the crankshaft，but had no influence on the starting power. The matching method of starting motor considering the efficiency of wedge-cam mechanism was put forward. The study will provide important base for performance analysis of internal combustion pump and design of starting system.