Abstract: According to the special requirement of optical instrument to the uniformity of thin film thickness on infrared window, Femm42 software was adopted to analyze the potential in the vaccum of radio frequence plasma enhanced chemical vapor deposition system, by changing the height of DOME, and adding a metal ring behind the DOME, the problem of delamination on the edge of dome had solved. Taguchi experimental method was used to decrease times of experiment, at the same time, the secondary condition of effecting performance of thin film was found. The effects of the process parameters on the results of thin film thickness uniformity were analyzed. Finally, the optimal parameters had comfired. The DLC film that the uniformity is less 3% and can endure the bad environment test had successfully prepared.