Abstract: The dynamic analysis of main body and valve type orifice system was conducted and the dynamic models were developed for studying external characteristics of three-cylinder internal combustion water pump. Fuel consumption, effective thermal efficiency and running unevenness at full throttling were simulated through AVL Boost and MATLAB software. The curves of simulation were drawn. The external characteristics of three-cylinder internal combustion water pump were compared with those of engine driving pump system. The results show that fuel consumption and running unevenness of three-cylinder internal combustion water pump are higher than those of engine driving pump system while effective thermal efficiency of three-cylinder internal combustion water pump is less than that of engine driving pump system. Within 1600～1800 r/min of higher volumetric efficiency, fuel consumption was 17 percent lower than engine driving pump system. Fuel consumption at full throttling was tested and compared between experiment and simulation. Relative errors were all within 5 percent and it proved that the models and simulations were correct.