Flue-gas desulfurization is the main method of coal desulfurization. In this study, a potassium humate (KHA) solution was used to remove SO2 from flue gas, and the effects of the KHA concentration, solution temperature, SO2 concentration and oxygen content on SO2 absorption efficiency were explored. The results showed that the desulfurization performance of KHA absorbent is much better than that of an equal volume of water or potassium hydroxide solution with the same initial pH. The SO2 concentration, reaction temperature and oxygen content greatly influence HEDT (high-efficiency desulfurization time). When the concentration of KHA is between 0.024-0.120 g/L, HEDT increases as the KHA concentration increases; after desulfurization, the KHA product is poorly soluble in water and is easy to separate. Implementation of the desulfurization process by KHA mainly involves providing alkalinity and pH buffering agents in the desulfurization process.