Choosing Al86Ni6Y4.5Co2La1.5 amorphous powder and adopting self-developed low-temperature supersonic spray system, the paper has prepared the aluminum-based metallic glass coating on ZM5 surface with good corrosion resistance, analyzed the pores’ types and causes in the coating, selected the X-ray three-dimensional imaging method for the determination of the coating’s porosity and the characterization of the pores’ geometry features, clarified the influence of pores on the corrosion behavior of the coating. The results show that the coating consists mainly of four types of conventional porosity defects，which are macro-type、layer-type、 microsphere-type and microscopic-type; The porosities are substantially less than 1% and have little change along the thickness direction, the pores are nearly spherical, and their average sizes are less than 10μm, especially about 5μm; different porosities in the coating are shown a wide range of self passivation interval, closer self corrosion potentials and positive correlation between the corrosion current densities and porosities. Individual special pores with the characteristics of large-size, through-type and at the border are the root cause of coating’s corrosion failure.