The SiC thin films as the window layer was prepared by PECVD technology in this article, investigated the influence of hydrogen dilution on the optical and micro-structural properties of SiC thin films, Analyzed optical band-gap,deposition rate and surface morphology under different hydrogen dilution ratio, found the optimal growth craft under the same conditions. The results showed that the optical band-gap of the window layer achieved the widest 2.2ev when hydrogen dilution rate was 6.25.