Nano-diamond slurry was got by mixing with Nano-diamond powder, ethyl cellulose and solvent in a certain quality. Then the mixed solvent was dropped on ultra-white glass which fixed on sol-gel glue rejection machine. The machine was set to 3000 r/ min. After sintering, Nano-diamond film was got. Sintered glass was treated as the window layer of solar battery, and then conversion efficiency and impact factor were tested through IV characteristics system. As Nano-diamond have many excellent properties, such as the stability of chemical properties, resistance of high temperature and corrosion. So Nano-diamond film was chose as the window of solar cell because of. The different window layers of solar cells were contrasted and analyzed. And the result of Nano-diamond film's self-cleaning function could be got. What's more, the conversion efficiency of the solar cell could be improved.