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 membranes are described. Monte-Carlo simulation method is 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 and inferior ion blocking ability than Al2O3 IBFs.It is proved that BeO is feasible as an ion feedback membrane.