The carry-loading capacity of the airtight structure is important for high-speed trains. The load of air tightness has been analyzed and universal mathematical model has been built. As a calculation model, the FE Model of the vehicle body for a type of high-speed train has been established and the modal, transient analysis has been done. Different influence of load parameters on the vehicle has been analyzed and compared to obtain the response characteristics of the structure. Finally, the strength of the train under different working conditions is verified, weakness is pointed out and suggestions based on the simulation test are given.