By taking the effect of Tool Influence Function(TIF) used in the NC program on the polishing accuracy for optical elements into account, the method how to obtain the optimized TIF based on the aspheric parameters to be polished and polishing pad parameters is proposed. As the key to calculate the TIF of aspheric elements is to obtain accurately the dynamic pressure distribution between polishing pad and mirror, this paper analyzes the pressure distribution between polishing pad and mirror by finite element method and obtains the TIFs in different positions on the aspheric surface by classic Preston equation and planet motion. The variation tendency of the pitch polishing pad in polishing an aspheric element is analyzed in different polishing positions based on the dynamic pressure distribution model. The TIF spot experiment is carried out on an aspheric element with a curvature of 1 000 mm. The result shows that the shape of TIF simulated by the theory introduced in the paper is more similar with that of the actual situation, and the Pearson correlation coefficient reaches 0.977. It concludes that the method can obtain the pressure distribution conveniently by changing the parameter of polishing position and can optimize the TIFs, which provides a theoretical basis for improving polishing efficiency and polishing accuracy.