Aiming at globoidal cam one-side machining errors in addition to programming error, there exists combined effects of a number of the original errors, such as, machine motion error, tool error, fixture error and et al. On basis of the analysis of the principle of one-side processing, the theoretical calculation synthetic model of the one-side machining profile normal error is established based on the multi-body system error modeling theory and spatial mechanism conjugate meshing principle. And by applying Newtons iterative method and simulations in Matlab, the law of comprehensive influence of each original error on globoidal cam profile normal error is revealed. The simulation results verify the correctness of the theoretical calculation error synthetic model, and a scientific proof is provided for further improving machining accuracy of one-side machining of globoidal cam.