Based on the designed model of diesel engine with GT-Power software, the modeling characteristics were determined by combining with the structure of highaltitude simulation system, and the model was verified by comparing between simulated and tested results. Then the model was used to analyze the influence of high-altitude pressure and temperature on the intrinsic performance of diesel engine at high altitude. The effect of intake and exhaust pipe system on diesel engine performance was studied. The results show that high-altitude pressure has a greater influence than high-altitude temperature. The output power has a non-linear relationship with air pressure at high speed and will reduce with the decrease of simulated pressure. Diesel engine has a better performance with the decrease of temperature, especially at the speed lower than 1 800 r/min. Diesel engine will run well if intake pressure is higher than exhaust pressure and output the power of 10 kW per unit of increased pressure at best at the speed of maximum torque. Conversely, the performance of diesel engine will deteriorate if intake pressure is lower than exhaust pressure. Diesel engine can continue to run normally at a certain back pressure at medium and high speed, but cannot continue at medium and low speed. The length, diameter and roughness of intake pipe all have the effect on power output and the influencing degree from high to low was diameter, length and roughness. As for the exhaust pipe, the diameter is the main influencing factor. The critical diameter value is 0.2 m for both intake and exhaust pipes.