NOVELTY - Producing chlorine-free compound fertilizer, involves: adding mixed acid formed by phosphoric acid and sulfuric acid in a reaction device, adding potassium chloride, and reacting for 0.5-6 hours at 100-350 degrees C to obtain slurry with potassium dihydrogen phosphate/potassium bisulfate/gas hydrogen chloride; adding the slurry in ground phosphate rock; fully mixing, reacting and aging to obtain the mixture with potassium dihydrogen phosphate, potassium sulfate, calcium bisulfate and calcium sulfate; pelleting the mixture; and drying/cooling/sieving to obtain the fertilizer.    USE - For producing chlorine-free compound fertilizer (claimed), which is suitable for different crops, particularly medium and high-grade economical crops.    ADVANTAGE - The method produces the fertilizer with total nutrient of the chlorine-free compound fertilizer is greater than or equal to 25% and the chlorine is less than or equal to 3%. The production process uses wet production of phosphoric acid, potassium chloride low temperature conversion bisulfate, monopotassium phosphate production process so as to produce chlorine compound fertilizer. The production cost is low. The production technique is compact, short process flow, low investment, low reaction temperature, low energy consumption and low cost.    DETAILED DESCRIPTION - Producing chlorine-free compound fertilizer, involves: adding mixed acid formed by phosphoric acid with a mass concentration of 18-85% and sulfuric acid with a mass concentration of 30-100% in a reaction device; adding potassium chloride, and reacting for 0.5-6 hours at a temperature of 100-350 degrees C to obtain the slurry with potassium dihydrogen phosphate and potassium bisulfate and gas hydrogen chloride; adding the slurry obtained in first step in the ground phosphate rock; fully mixing, reacting and aging for 0.5-240 hours to obtain the mixture with potassium dihydrogen phosphate, potassium sulfate, calcium bisulfate and calcium sulfate, where pH of the mixture is 2-8; pelleting the mixture obtained in second step; and after pelleting, drying, cooling and sieving to obtain the chlorine-free compound fertilizer, where the total nutrient of the chlorine-free compound fertilizer is greater than or equal to 25%, and the chlorine is less than or equal to 3%; crushing the sieved small particle and big particle; and returning material.