Abstract: The metal porous material has been widely used in gas-solid separation, due to its excellent filtering performance and good physical and chemical properties. This research adopted the helium mass spectrometer leak detector, scanning electron microscope (SEM) and specific surface area analyzers etc. to analyze the porosity, microstructure,pore characteristic and distribution etc. of the iridium porous material. The results showed that the iridium porous material with interconnected internal pores and complex 3D structure was composed of iridium powder particles and pores. The porosity of the iridium porous material was about 16.93%. The pore diameter of 98.7% pores of the iridium porous material was between 0.002 to 0.05 μm, and the rest pore diameter was 0.05 to 0.46 μm. According to the filtering theory of porous material and particle capture theory (The thickness of the porous material is not considered), when the diameter of powder particles was not less than 0.46 μm, the filtration efficiency of iridium porous material reached to 100%. In addition, when the diameter of powder particles was less than 0.46 μm and the gas flow speed was no more than 5.28 m/s, the filtration efficiency of iridium porous material reached to 100% as well. However, when the gas flow speed was more than 5.28 m/s, part of powder particles (less than 0.46 μm) would pass though the iridium porous material. Obviously, it provides a novel approach for evaluating the filtration performance of porous materials by using filtering theory and particle capture theory. In addition, the iridium porous material can be used for the gas-solid separation in certain special fields, such as gas-solid separation of radioactive isotope materials.