Controlled-release fertilizer,especially polymer-coated urea (PCU),is more popular nowadays and holds a big potential agricultural market.Relative PCU products come out quickly.Although laboratory measurements of PCU N release characteristic are listed by most of the manufacturer,data from field condition,especially rich land with high moisture,are lack.Traditional weight method with a vacuum oven was usually used in evaluation of PCU N release.However the temperature and time were showed differently in different researches.An improved weight method was applied in this project: PCU particles in the mesh bags were washed with distilled water and removed to a plastic ziplock bag which was weight before.After then the bag is placed in a refrigerator at -80℃ for 2h,and then transferred to the lyophilizer for drying 24h.We compared this improved method with chemical analyses for Kingenta PCU (Shandong Kingenta Ecological Engineering Co.,Ltd.).Overall,regression analysis suggested the N release as determined by the improved method and spectrophotometry method was not significantly different over the growing season,which showed the improved weight method can be applied for determining PCU N release characteristics in rice land.