The removal function test is carried out on the earlier round-pellet polishing pad. The concept of filling factor is introduced to evaluate the removal function obtained from the experiments mentioned in the paper. To improve the filling factor and characteristics of the polishing pad, the pad structure is optimized according to the experimental results of the round-pellet pad. The removal function of the new polishing pad is simulated with MATLAB. The stability experiment is carried out in full aperture at the same time. The fixed abrasive and the slurry abrasive polishing experiment both are performed under the same conditions. Finally, the structural similarity index is introduced to evaluate the similarity between simulations and experiments. The best structural similarity index of multi-square-pellet pad is 0.4257. The comparison results are acceptable and positive. The optimized fixed abrasive polishing pad is proved to be highly promising for large-diameter SiC mirror fabrication.