Abstract: Effect mechanism of PPD is described, including crystal nucleus, adsorption and eutectic. Water-base PPD BEM-6N is synthesized with emulsification method. Taking Daqing Crude Oil and Qinghai Crude Oil as experimental objects, influence of PPD morphology, heat treatment time and temperature on effect of PPD is researched. The paper compares and analyzes PPD evaluation results from laboratory testing and field testing, and considers that laboratory evaluation results of PPD exists a certain limitation and it is uncertainly rational to thin the PPD into organic solvent with lower mole fraction. Suggestion on laboratory evaluation method and field application for water-base PPD BEM-6N is proposed that the set point of the PPD should be lower than the inlet temperature of oil pumps.