K-feldspar (KAlSi3O8) is a major potassic aluminosilicate mineral in nature, and its total reserves are up to 4.641 billion tons in China. Up till now, however, there still exist many difficulties in using this resource directly as potash fertilizer in agriculture due to its high insolubility. In order to decrease the calcination temperature and shorten the calcination time for transforming K-feldspar into soluble potash salt and hence reducing the production costs, this paper has discussed the influences of the addition of four types of fusing agents on the KAlSi3O8-CaSO4-CaCO3 system and selected the most favorable fusing agents. The transformation ratios from K-feldspar mineral to soluble K2O in the KAlSi3O8-CaSO4-CaCO3 system under different calcination conditions were detected systematically. A simulation calculation on such a basis demonstrated that the solid diffusion dynamical process in this reaction was in accordance with the Ginstling dynamic equation, with its apparent activation energy Ea being 128.92 kJ/mol. Four types of fusing agents, namely Na2SO4, Na2SO3, NaCl and NaF, were added into this reaction system respectively by 3%, 3%, 3% and 1% of the total mass of reactant, and the value of the apparent activation energy Ea was decreased from 128.92 to 87.15, 98.71, 117.38 and 126.14 kJ/mol in turn. It is thus shown that Na2SO4 may be the most favorable fusing agent, which can reduce apparent activation energy Ea, decrease reaction temperature effectively and speed up solid diffusion velocity in the KAlSi3O8_CaSO4-CaCO3 system.