Excimer laser plays an important role in the national economic production because of its short wavelength, high repetition frequency and large energy. In the output characteristics of excimer lasers, high beam quality and high energy stability are the characters of high-end excimer light source, and whether the excimer laser system can sufficiently develop the preionization process is the key to output laser pulses with high beam quality and stable energy. This paper is mainly to study the preionization process of ArF excimer laser, and establish one-dimensional simulation calculation model and two-dimensional simulation calculation model. Based on the fluid calculation method of Comsol Multiphysics software, the numerical simulation analysis and calculation are carried out, with the study focusing on the ionization wave propagation process in the preionization process and the relationship between preionization and main discharge. The results show that the spatial structure of corona rod and main electrode should be considered comprehensively when an excimer laser system is designed. Appropriate preionization structure and voltage can make the main discharge triggered during the maintenance of free electrons, which can effectively reduce the discharge voltage, avoid streamer and arc discharge, and improve the output beam quality and system energy stability.