In order to reduce the problem of image quality degradation caused by stray light in the optical system， polycarbonate is used as the substrate and the electron beam ion assisted method is used to prepare the ultra-low attenuation reflective film in visible band. Vacuum annealing method was used to reduce the thermal tensile stress caused by the increase of substrate temperature in the coating process， and MATLAB software was used to fit and analyze the stress of the material. By studying the ion source deposition process， the problem of film cracking was solved. MATLAB simulation was used to adjust the control parameters of Proportion Integration Differentiation（PID） controller ， so as to stabilize the film-forming rate and solve the problem of spectral drift caused by thickness error. The results show that the absolute reflectance of the film is less than 0.15% at 430 ~ 700 nm.