As an important factor the error of mask pattern is often ignored in the lithography simulation model. To investigate the impact of mask errors on the lithographic pattern, effects of how the wave-front on different mask pattern region affects the field points in resist is first introduced, and based on this analysis a method is proposed to quickly judge the affection of round corner error of mask pattern on the photo-resist pattern. By comparing the actual effect area and the effective wave-front area around the corner on mask pattern, the method can illustrate the quantitative relationship between variation in photo-resist pattern and the related mask error. Finally the simulation results are verified by experiments. The study results may contribute to the fast and accurate judgments of error in the lithography, and provide important theoretical basis for lithography error correction.