Abstract: The mechanism of activated reaction in preparing of desulfurizer, from coal Was studied. By analysing reaction products and calculating the mass transfer resistance, the mechanism of activated reaction was the reaction of water with hydrocarbon molecules which were expelled during carbonization process and adsorbed on the surface of micro-pores of particles. As a result of the reaction, the surface of micropores of the desulfurizer was cleaned, and the specific surface area and adsorp-tive capacity of the desulfurizer were improved.