In order to improve the grinding efficiency of screw rotor, a screw synchronous grinding device is developed. Different ways are used to grind the concave and convex sides of screw respectively, which will produce repeated grinding areas at the joints. In order to ensure that the surface quality of the repeated grinding area meets the requirements of the screw, the surface roughness of the area is predicted. Firstly, based on Rayleigh distribution, the abrasive particle distribution model on the surface of sand belt is established. On this basis, the surface morphology of the ground screw is predicted according to the grinding removal mechanism and screw profile. Secondly, according to the definition of surface roughness profile, the predicted values of surface roughness under different process parameters are obtained. Finally, the accuracy of the proposed algorithm is verified by screw grinding and measurement experiments. The experimental results show that the average error of the proposed algorithm is 6. 27% and the minimum error is 0. 16%. Therefore, the proposed algorithm can provide a theoretical basis for the prediction of surface roughness in screw rotor abrasive belt grinding.