The invention relates to a method for producing monopotassium phosphate, which comprises the following steps of: 1, dissolving potassium chloride and phosphoric acid into water so as to prepare the mother liquid of a product; and dissolving ammonia and ammonium chloride into the water so as to prepare the mother liquid of a by-product; 2, extracting the mother liquid of the product by using an extraction agent in a micro-mixer and then separating so as to obtain a loading extraction agent and raffinate; 3, cooling the raffinate so as to precipitate monopotassium phosphate crystals and then carrying out solid-liquid separation, wherein solid is the product, and liquid is the mother liquid of the product for recycle; 4, carrying out back extraction on the loading extraction agent by using the mother liquid of the by-product in the other micro-mixer and then carrying out phase separation so as to obtain a regenerating extraction agent and back extraction liquid; and 5, recycling the obtained regenerating extraction agent, cooling the back extraction liquid so as to precipitate ammonium chloride crystals and then carrying out solid-liquid separation, wherein solid is the by-product, and liquid is the mother liquid of the by-product for recycle. According to the method for producing the monopotassium phosphate, cross pollution caused because of the problems of carrying and selectivity of the mother liquid of the product and the mother liquid of the by-product is avoided by process control, the extraction process and the crystallization process are decoupled by equipment reinforcement so as to avoid the generation of fine crystals, and monopotassium phosphate with high quality can be produced.