An engine cooling system of heavy vehicle was used as a research object in this thesis. Engine system model was designed with KULI software according to wind tunnel testing data of heat exchanger provided by supplier. Simulation calculation provides optimization program based on the results. The result is that it can simulate calculation with KULI software, in the early design on a cooling system of heavy vehicle engine. The study provides a theoretical basis for the design of a cooling system of heavy vehicle engine, improve the efficiency and save the cost.