According to the technical requirements of the immersion lithography system, the beam stabilization system was designed through eliminating the positional drift and the pointing drift of the beam by two mirrors. Based on the characteristics of deep ultraviolet materials, JGS1 was chosen as the substrate of the mirror, and Al2O3 and MgF2 were chosen as high and low refractive index thin film materials respectively. The design and simulation analysis of high-reflection film were completed through the film design software, and the film was developed by vacuum deposition technology. The non-uniformity index of the film was ensured to be less than 0.2%by selecting the planetary fixture coating equipment and designing the specific compensation baffle. The spectrum curve and the surface microstructure of the mirror sample were tested. The results show that the developed film has a reflectance of 98.5% at 45° incidence and a scattering loss of 0.30%, which satisfies the system requirements.