The illumination system is an important part of the projection lithography exposure optical system. Its function is to provide high uniformity illumination and control the exposure dose and different illumination modes for the mask surface. As an important part of the lithography lighting system, the zoom system plays a vital role in improving the performance of the entire lithography machine. According to the characteristics of the ultraviolet lithography illumination system, this paper uses CODE V software to complete the design of the zoom system in the near ultraviolet lithography illumination system with a wavelength of 365 nm, an entrance pupil diameter of Φ33 mm, an image telecentricity ≤10 mrad, and a distortion ≤±2%. The effect of the error source of the zoom system on the pupil performance of the system is analyzed, combined with the design scheme of the zoom system and the actual processing capability, gives a single-sided thickness tolerance of less than 20 μm, a moving part movement accuracy of less than 0.5 nm, and an eccentric tolerance of less than 0.02 mm for each lens. The tilt tolerance of each lens is controlled within 1′. The tolerances are reasonable and feasible, and meet the requirements of high uniformity and high energy utilization of the UV lithography illumination system.