With further improving the speed of high speed train,the air flow on the train’s surface is altered.The operation condition of its air conditioning unit is also changed,which at last,will affect the performance of the air conditioning unit.The air flows on the surface of high speed train in different conditions were simulated by using the software of FLUENT.The distribution of the air pressare on the surface of high speed train and the pressure values at its specific locations were obtained.The effects of raising the train speed on its air conditioning unit’s operation parameters,like the pressure of condenser fan,condensing air volume,condensing temperature and refrigeration coefficient were analysed.The conclusions provide certain theoretical basis for the optimization design of high speed train’s air conditioning.