In order to improve the accuracy of the deformation calculation of the slender shaft in the machining process, a simulation method of the slender shaft cutting process considering the coupling effect of cutting heat and cutting force is proposed in this paper. The convection heat transfer coefficient of the slender shaft is solved by analyzing the convection heat transfer in the cutting process of the slender shaft.Finite element method is used to simulate the actual cutting process of the tool and extract the cutting force.Temperature load and cutting force are loaded on the slender shaft at the same time to accurately analyze the deformation of slender shaft under the action of thermal coupling. The results show that the analysis provides a theoretical reference for effectively analyzing the deformation of slender shaft under complex boundary conditions in engineering.