Abstract: The effects of combustion temperature and biomass blending ratio on the release of K, the occurrence form of K in the ash and the change of mineral matter were studied. It is found that combustion temperature has a significant effect on the release of K. At 600-750℃, with an increase in temperature, water-soluble K and NH₄Ac-soluble K are released to the gas phase, which makes the release ratio of K fast; while at 750-850℃, water-soluble K and NH₄Ac-soluble K begin to convert into other forms of K and are fixed in the ash sample, which makes the release rate of K slow; when the temperature is higher than 850℃, as the temperature increases, the decomposition of HCl-soluble K causes the release rate of K increase again. Through XRD analysis, it is found that the water-soluble K in ash mainly exists in the form of KCl. The production of K₂SO₄ is affected by both the K content in the raw material and the S/Cl ratio, the higher the content of K in raw materials, and the greater the ratio of S/Cl, the more it will promote the formation of K₂SO₄. At the same time, it is also found that there is a synergistic effect between biomass and coal combustion. The elements such as Al, Si in coal may react with K in biomass to generate alkaline aluminosilicate, resulting in more K remaining in the ash.