Piezoelectric material lithium niobate (LiNbO3) can be used as the piezoelectric layer in SAW devices,however the thickness of LiNbO3 crystal is usually 500 μm，actually the valid thickness varies from λ to 2λ. In order to realize the hybrid integration of SAW devices,LiNbO3 wafer need to be processed using the bonding and thinning technique.The sample of LiNbO3 crystal was chemical polished by using silicon dioxide solution of grain size 100 nm. The influence of polishing plate, polishing plate speed，pressure and polishing time on the polishing quality of LiNbO3 crystal were investigated. The optimum parameters were as follows. Polishing should be carried out using a polishing cloth and silicon dioxide solution of grain size 100 nm, a polishing plate speed of 120 r/min, a pressure of 3.9 N, and a polishing time of 40min. It was tested that thickness of the sample was 80 μm，optimal roughness Ra=0.468 nm and Rq=0.593 nm.