SiO2 films are deposited on Al2O3、 JGS3 and Si substrate by electron beam technology. In-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and atomic force microscope (AFM) tests are used to demonstrate the relationship between the water absorption and the microstructure of the SiO2 films. The in-situ DRIFTS and AFM results indicate that the water absorption is enhanced while number of pores on the film surface increased. The peaks of absorption center is determined by the surface roughness of the films. Blue-shifted of absorption are evidently observed while the temperature increased from 25 ℃ to 220 ℃.