The characteristics and principle of deliquescent polishing technology for potassium dihydrogen phosphate (KDP) crystals are introduced, and the performance requirements of deliquescent polishing fluid for KDP crystals are proposed. The main components of the deliquescent polishing fluid for KDP crystals were selected according to these performance requirements. Through uniformity experiment, stability experiment and fluidity experiment, uniformity, stability and fluidity of deliquescent polishing fluid for KDP crystals prepared using the selected components were tested. Through deliquescent polishing experiment of KDP crystal, polishing performance of deliquescent polishing fluid compounded using the selected components was tested. The material removal rate of the KDP crystal in the deliquescent polishing experiment was 6.03μm/min, and the surface roughness of the KDP crystal after deliquescent polishing was 4.857nm. The experimental results show that the compounded deliquescent polishing fluid for KDP crystals has good polishing performance and can reach the requirements.