Based on the strong oxidation property of H2O2 solution, a simple and practical method for surface modification of PMMA substrate was explored. The mechanism of H2O2 on PMMA at room temperature and hydrothermal conditions was studied, and the effect of surface modification on the interface adhesion between PMMA substrate and SiO2 coating was investigated.PMMA substrates were treated with different concentrations of H2O2 solutions at room temperature or under hydrothermal conditions. Changes of surface chemical composition of PMMA before and after modification were measured by infrared spectrometer (FTIR); the light transmittance of sample was characterized by ultraviolet-visible spectrophotometer (UV-Vis); the surface wettability of sample was evaluated by the measurement of water contact angle. SiO2 coating was prepared on the surface of PMMA substrate by magnetron sputtering method and sol-gel method, respectively. The microscopic changes of surface morphology were analyzed by material microscope and atomic force microscope (AFM), and the coating adhesion was evaluated by cross-cut and friction test. The surface treatment conditions of PMMA substrate were 30wt% H2O2 solution, hydrothermal temperature 60 ℃ and time 1h. The water contact angle decreased from 73° to 56°. AFM analysis showed that H2O2 removed the passivation layer of PMMA, and the SiO2 particles deposited by magnetron sputtering were of regular shape, uniform and compact. The visible cracks on the surface of coating prepared by sol-gel method changed from more unmodified, less modified at room temperature to no hydrothermal modification. Cross-cut tests showed that coating prepared on the surface of hydrothermally modified PPMA did not fall off and was evaluated as grade 0. Hydrothermal treatment of PMMA substrate with high concentration H2O2 solution improves its surface wettability and improves the interfacial adhesion between PMMA and SiO2 coating. SiO2 coating prepared on the surface of modified PMMA is composed of uniform and dense nanoparticles, which has a certain protective effect.