The formation of super-thin continuous dielectric film (e.g. the ion barrier film-IBF) on microchannel plate (a kind of porous substrate) is most important for prolonging the operating life of the third generation micro-light image tube. In this paper, firstly, the formation of Al2O3 ion barrier film on microchannel plate (MCP) using a new contamination-free technology was introduced. According to the analysis and the comparison with the traditional direct formation technology, it was found that the productivity of the new technology is better (90%) and the carbon contamination can be minimized. Next, the stopping and transmittance characteristic of the film for electrons were studied and the measurement principle was shown. In this measurement, the concepts of “dead-voltage” and “electron transmittance” were proposed to evaluate the stopping and transmittance of the film for electrons. The dead-voltage was 220V for the MCP covered the ion barrier film with a thickness of 5nm and the electron transmittance was over 90%.