Abstract. This paper is based on the theory of computational fluid dynamics (CFD), the turbulent flow field of turbocharger is numerically simulated by fluid-solid coupling method, and the flow field cloud of the turbine is obtained. By comparing the calculated efficiency and experimental values, we can see that the error between the two does not exceed 5%. The simulation accuracy is verified. Through the improvement of the turbine blade through the three-dimensional modeling software, the modified turbine is re-simulated. The results show that the improved turbo expansion ratio is improved by 0.05 and the turbine efficiency is improved by 4.55%.