In order to analyze the influence of different etching liquids on residual salt，etching experiments on the surfaces of polished fused silica samples are designed and carried out. The surface morphologies of different etched samples are investigated by high magnification optical microscope and profilometer，and the residual salts are detected by X-ray photoelectron spectroscopy（XPS）. The results show that only a small amount of polished defects are exposed on the surface of the sample treated with a etching liquid containing sulfuric acid，with a surface roughness of Ra 0.014 6 μm、Rq 0.025 2 μm. The surface element detection results are highly similar to the non-etching sample，and no F element is detected. According to the analysis，adding sulfuric acid to the etching liquid will promote the dissolution of the fluorosilicates during the reaction process，which is more couducive to obtain a smooth and flat etched surface.