Low solubility poly carbonyl urea has been successfully synthesized by the reaction of urea with methyl carbamate (MC) under the conditions of potassium carbonate as an initiator. It was characterized by FT-IR, 13C-NMR, and elemental analyser. In addition, the influences of the quantity of initiator, reaction temperature, reaction time and the molar ratio of starting materials on the conversion are discussed in detail. All those observations suggest that when initiator as 10 wt % of urea, the reaction temperature 160?, 6 h, and n(urea):n(MC)=1:10, the reaction conversion rate can reach 78.4%. Moreover, the novel procedure is reported for the first time and has a significant N slow release properties, the N release in soil was 80% over 30 days.