Technological aspects of a new method of obtaining magnesium phosphate based on the interaction of magnesium chloride from liquid waste from the processing of potassium ores and sodium phosphate have been studied. The influence of precipitation conditions of magnesium phosphate crystal hydrate, washing of the obtained precipitate and its drying on the yield and product quality was studied. Rational technological parameters of realization of the main stages are chosen. The developed technological process, in comparison with the known ones, allows to simplify the technology, reduce the cost of production, balance the composition of liquid waste for further processing into potassium-magnesium fertilizers.