Abstract: Aiming at the damage of booster thrust bearing during the switching process of sequential turbocharging system,in order to improve the stability of the supercharger during the switching process,this paper takes a certain type of supercharger as the research object,and builds a three-dimensional model of the supercharger.The grid is divided by Fluent and the flow field of compressor and turbine is numerically simulated.The variation law of axial force of turbocharge under typical switching conditions of sequential turbocharging system is analyzed.The results show that during the switching process of the sequential turbocharging system,the longer the transient switching time,the greater the proportion of the fluctuation time of the axial force.During the switching process,the greater the transient speed change of the supercharger,the smaller the proportion of axial force oscillation and the higher the final axial force.The major factors influencing the axial force change of the supercharger include the gas leakage of the wheel back,the switching time and the speed change.