The profile accuracy of screw rotor affects the performance of screw compressor directly. In precision form grinding, installation errors of grinding wheel are the crucial factors affecting profile accuracy of screw rotors. A numerical method for quantifying profile error of screw rotor was proposed to evaluate effects of installation errors of grinding wheel on rotor profile. Coordinate transformation and engagement theory were applied to generate rotor profile, and the error model of rotor profile was established by comparing the generated rotor profile with the original one. Furthermore, the error evaluation procedure was presented based on the discrete rotor profile points. Three kinds of installation errors of grinding wheel are analyzed including installation angle error, center distance error and axial position error in the numerical cases. By inputting installation errors of grinding wheel, the effects on rotor profile are evaluated considering both single-factor installation errors and coupled-factor installation errors of grinding wheel. The evaluated results provide a theoretical basis for error tracking and error compensation in screw rotor grinding. Grinding experiments were performed for female rotor with different installation errors. The experimental results verify the correctness of the evaluated results.