Abstract: The influence of thesmoothprofile of a straight-claw rotoron the behavior of the claw vacuum pump:including the meshing, sealing, and distributions of stress and deformation of the cusp-free rotors, was empirically approximated, mathematically formulated with 3-D model, theoretically analyzed and numerically simulated with COMSOL software for design optimization. The simulated results show that the claw-head arc angle, shape factor, and meshing clearance of the cusp-free rotor all have a major impact. To be specific, the optimized cusp-free rotor profile comprises a claw-head arc angle in 20° ~ 60° range, a shape-factor reduced to 0. 6 ~ 0. 7, and a meshing clearance of 0. 110 mm. We suggest that the simulated results may be of some technological interest in design optimization of the claw vacuum pump with cusp-free straight claw rotors.