The invention relates to the technical field of wastewater treatment, in particular to a method for extracting and refining a potassium salt from mica acid production wastewater. The method for extracting and refining the potassium salt from the mica acid production wastewater comprises the following steps: firstly, concentrating the mica acid production wastewater, and adjusting the heat value and the pH value of the mica acid production wastewater; controlling the temperature of a high-temperature liquid incinerator to be 600-1200 DEG C, spraying the pretreated wastewater into the high-temperature liquid incinerator for high-temperature decomposition, performing high-temperature denitration on generated gas, performing desulfurization, performing absorption, performing water washing treatment, performing emptying, and recycling incineration residues at the bottom of the incinerator; and finally, adding water into the incineration residues for dissolving, performing filtering, performing concentrating, and performing crystallizing to obtain the potassium salt. According to the method provided by the invention, the potassium salt in the wastewater is extracted in the wastewater treatment process, the equipment investment costs of the whole process are low, the wastewater treatment costs are low, the recovery rate of the potassium salt is high, and the purity of the recovered potassium salt is high.