Abstract: Underground Coal Gasification （UCG） is a pivotal technology for clean coal utilization and supplementing natural gas supplies. While catalysts significantly enhance gasification efficiency and syngas quality, their effective delivery into deep underground reaction zones remains a technical challenge. To explore the appropriate catalyst injection process, Ansys Fluent was adopted to simulate the multiphase flow characteristics of catalyst injection, analyzing the effects of transport media, particle diameter, inlet particle concentration, inlet velocity, and pipe cross-sectional area. The simulation results indicate that: Regarding transport media and particle characteristics, smaller particle diameters and concentrations enhance the carrying capacity, with pure water demonstrating superior carrying performance compared to oxygen. In terms of pipe structure and operating conditions, increasing the pipe cross-sectional area enhances injection efficiency, while reducing inlet velocity mitigates centrifugal forces on particles at pipe bends, thereby improving outflow efficiency. To ensure successful injection, the particle diameter should not exceed 0.43 µm when using oxygen as the medium, and 1.3 µm when using pure water. These findings provide theoretical guidance and optimized parameters for the engineering application of catalytic UCG.