The work aims to investigate effect of surface roughness of cemented carbide inserts on residual stress distribution of workpiece surface. Firstly, a three-dimensional oblique cutting model was established based upon AdvantEdge FEM software, and a tool-chip friction model was obtained. Then, surface of the cemented carbide inserts was pretreated in the method of chemical mechanical polishing (CMP), and cemented carbide inserts of different surface roughness were prepared. Cutting force was obtained by performing four factors-four levels orthogonal cutting experiments to the inserts of different surface roughness. Tool-chip friction coefficient was obtained according to experimental results of cutting force and tool-chip friction model. Cutting residual stress was simulated based on the AdvantEdge FEM software. Finally, rationality of the simulation model was verified by performing experiments. The maximμm residual stress of the workpiece surface was 621.51, 655.46, 654.69, 687.29 MPa when the cemented carbide insert with surface roughness of 0.02, 0.04, 0.08, 0.2 μm was used to cut 45 steel. Cemented carbide insert with surface roughness of 0.02 μm was compared with the cemented carbide insert with surface roughness of 0.2 μm, the maximμm residual stress of the workpiece surface decreased by 10.58%. The better the surface quality of cemented carbide insert is, and the lower the surface residual stress is.