Abstract: GGG(gadolinium gallium garnet)wafer is an excellent kind of laser material.However,its surface is easily scratched and the efficiency low during the polishing process.In order to avoid the scarification and improve polishing effect,polyurethane polishing pad was used to mechanically polish the GGG wafer.The influences of working pressure and plate speed on the flatness and surface quality were researched.Resultsshow that the polyurethane polishing pad could avoid the appearance of scarification efficiently and that smaller abrasive is better for the flatness.Under the optimized parameters(70r/min and 127g/cm²),the flatness could reach 226 nm,with surface roughness RMS36.3nm and the defects of the surface could be easily eliminated by chemical mechanical polishing.