The aspheric computer numerical control (CNC) grinding machine developed in the lab was taken as a research object. The geometric errors of the machine, homogeneous transformation principle and multibody system theory were systematically analyzed. The comprehensive error model which contained all the geometric errors of the machine was built.Based on the dualfrequency laser interferometer, the complex equation with single error as a variable of the machine was built by applying 9 lines error identification method and rotary error identification method, and the branch value of each error was calculated. According to the characteristics of aspheric CNC grinding machine of positioning error，the incremental principle of error compensation was proposed. The research results show that the principle of error modeling and compensation can effectively improve the positioning precision of the aspheric CNC grinding.