The work aims to study erosion effect of environmental factors including temperature, humidity, ultraviolet and atomic oxygen radiation on polyimide films and coatings by treating polyimide in different surface modification methods. The polyimide films were treated by alkaline solution (NaOH) under hydrothermal condition and silane coupling agent (KH-550) under solvothermal condition respectively. Silica sol was prepared in sol-gel method, and silica coatings were prepared on the modified polyimide films. Hydrophilicity, transmittance, surface morphology and surface structure change of the modified polyimide films was characterized by contact angle meter, ultraviolet visible spectrophotometer, scanning electronmicroscopy (SEM) and Fourier transform infrared spectrometer, respectively. Environmental effect test was evaluated with ultraviolet accelerated weatherometer and atomic oxygen simulator. The effect and destructive effect of environmental factors on the coatings were characterized with SEM and material microscope. The optimum surface treatment conditions were obtained: (1) 0.1 mol/L NaOH solution under hydrothermal condition at 120 ℃, 60 min; (2) 20vol% KH-550 + 80vol% EtOH under solvothermal condition at 180 ℃, 60 min. Interface between the polyimide substrate treated under the above conditions and silica coatings was bonded securely. The interface adhesion between polyimide substrate and SiO2 coatings can be effectively improved in surface modification methods of alkali hydrothermal treatment combined with silane coupling agent solvothermal process. The prepared silica coatings are homogeneous and dense, and resistant to atomic oxygen attack. However, destructive effect of environmental humidity on the coatings during the process of storage and transportation must be noted.