Diesel engine quasi-dimensional model were corrected by test in plateau. The full-coupled working process simulation model with variable altitude adaptation on certain heavy-duty vehicle propulsion (diesel engine and auxiliary system) was set up. According to the quasi steady state flow uniformity resistance and heat transfer equations, air intaken system resistance model were established. Based on 1-D unsteady compressible fluid dynamics theory and heat transfer theory, the working model of fuel injection system was erected. Considering the effect of lubricating oil on heat transfer, the engine cooling system model was established. Auxiliary system model and the working process of the engine were coupled, that means, the boundary conditions was two-way delivered. Simulation model were verified by experiment. The results show that the power reduces by 45% and fuel consumption increases by 71% at maximum at 4500m altitude under external characteristic working condition. The heat quantity of cooling liquid in heat-flux distribution increases by 48.6%. The temperature field of piston-cylinder sleeve-cylinder head raises apparently, the peak temperature increases by 85～91K. The delivery lift of water pump drops by 3.9m at most at 3700m altitude. When the water flow grows up, the thermal load of cooling system raises.