Ammonia volatilization is an important way of nitrogen loss in calcareous soil.Severe ammonia volatilization will lead to a waste of nitrogen fertilizer resources and atmospheric environmental pollution.A field experiment was carried out to test ammonia volatilization of the winter wheat growing stages and winter wheat yield affected by nitrogen fertilizer synergists in a calcareous fluvo-aquic soil of Xuchang county，Henan Province.The field experiment was designed with four treatments:CK(without nitrogen fertilizer applied)，urea only(U)，urea with urease inhibitor(URI)and urea with nitrification inhibitor(NIF).The results showed that the peak value of soil ammonia volatilization rate of different treatments appeared at 3rd week after fertilization，and it ranked as U>NIF>URI>CK.The maximum value of soil ammonia volatilization rate of the U treatment was 2.27% higher than that of the NIF treatment，and 21.84% higher than that of the URI treatment.The peak ammonia volatilization rate of the NIF treatment was 19.13% higher than that of the URI treatment.The order of ammonia volatilization accumulation of the four treatments during the winter wheat growing stages was CK