B2-structured Fe-20.5Al-18Cr (wt.%) intermetallic filter material developed for high-temperature coal-gas purification was fabricated by reactive synthesis using blended Fe/Al/Cr powders. This method addresses the problems presented in the manufacture of porous Fe-Al-Cr materials with high content of Al, making the production more convenient, flexible and controllable. The exothermic effect, volume swelling, pore formation and diffusion reactions during the reactive synthesis of porous Fe-20.5Al-18Cr were investigated systematically. A comparative study with porous Fe20Cr7Al material produced from prealloyed powders was carried out synchronously. The results show that during sintering the Fe-20.5Al-18Cr compact presents limited exothermic behavior and obvious volume expansion, and that the abundant pores and compositional homogenization can be obtained through the interactions of Fe/Al/Cr powders after final sintering. As compared with sintered Fe20Cr7Al porous material, porous Fe-20.5Al-18Cr possesses bigger permeability constants and lower oxidation and sulfidation rates. Pilot-scale filtration tests reveal that Fe-20.5Al-18Cr filter material can robustly serve in the corrosive H2S-contained and alkali-metals-oxides-loaded high-temperature coal gas during a period of 1000 h.