Aiming at the problems of small average particle size of potassium chloride crystal prepared by carnallite decomposition,resulting in large loss of filtration and washing and high energy consumption in drying,the effect of adding concentration of trisodium citrate,concentration of carnallite solution,stirring rate,residence time,volume and rate of carnallite solution on the particle size of potassium chloride crystal was investigated with trisodium citrate as nucleation inhibitor.Based on the single factor experiment,the Box-Behnken response surface optimization design method of three factors and three levels was used to study.The results showed that the average particle size of potassium chloride crystal was 595.892 μm under the conditions of adding 0.007 mol/L trisodium citrate,adding 0.759 g/mL carnallite solution,stirring rate of 372.52 r/min,residence time of 40 min,adding volume of 100 mL and adding rate of 2 mL/min,which was 1.69 times of the average particle size （351.607 μm） of the obtained potassium chloride product when trisodium citrate was not added and other experimental conditions remained unchanged.And the purity of potassium chloride product was 95.82%,which met the requirements of potassium chloride product quality standard of“Industrial potassium chloride” GB/T 7118—2008.The experimental results provided a reference for improving the particle size of potassium chloride products.