Abstract: The electron cyclotron resonance (ECR) discharge system, generating an electron beam, can effectively address the shortcomings of traditional thermal cathode electron guns, such as short lifespan and unstable performance. To investigate the characteristics of an electron beam source, a simulation analysis of an ECR discharge system operating at 2.45 GHz with a 100 W microwave input was conducted. Argon gas was used as the discharge gas, with processes such as collisions, excitation, and ionization incorporated into the simulation. An ECR discharge model was established to explore the variation of plasma parameters within the ECR plasma, such as electron density and electron temperature, under different working pressures, and to calculate the electron emission current based on these parameters. The results indicate that as the working pressure increased from 0.005 Pa to 0.04 Pa, the electron emission current increased from 60.5 mA to 85.2 mA, meeting the beam source requirements for processing. This study provides a reference for the design of ECR plasma cathode electron guns.