With the increasing demand for high-temperature gas filtration, porous intermetallic compounds have attracted much attention. In this study, high porosity CoAl with 3D microstructures was prepared using the thermal explosion. The link between the pore structure, mechanical and oxidation resistance of the product was established using 3D-XRM. Moreover, an oxidation corrosion test was conducted in fluid and static air at 700–900 °C for up to 120 h. During the rapid growth stage, the mass gain was dominated by the inward diffusion of O, while during the slow growth stage, it was dominated by the outward diffusion of Al.