The surface figures of 120 mm×88 mm samples were measured by ZYGO Mark Ⅲ-GPI interferometer before and after coating. The analyzed of peak to valley (PV) and gradient of root mean square (GRMS) show that PV and GRMS increased,respectively,after deposition. At the same time,GRMS increased with the increase of PV,which also can be confirmed from the theoretical calculation. In addition,the power spectral density (PSD) of several samples are also shown. The results indicate that the curves ascend after coating,which relates closely with the substrate and deposition condition.