Microchannel plate (MCP) with ion barrier films is the core component in Low Light Level (LLL) Image Intensifier tubes in Generation Ⅲ. In this paper, the electron transmittance and ion blocking properties of IBFs were described. Monte-Carlo simulation method was used to calculate the electron transmittance and ion blocking ratio of BeO and Al2O3 under different conditions. The simulation results show that BeO IBFs has better electron transmittance than Al2O3 IBFs, while Al2O3 IBFs has better inferior ion blocking ability than BeO IBFs. It is proved that BeO is feasible as an ion barrier film.