Abstract: The paper aims to explore the enhancement of nitrogen use efficiency and yield- increasing mechanism with applying coated urea only once. A field plot experiment was conducted to study the effects of different coated urea and bare urea on maize yield and transformation of three types of coated urea in soil. The results showed that: compared with applying bare urea, the application of coated urea could inhibit the activity of urease in soil in the early maize growth period, the inhibition rate of treatment 3, 4, 5 was 27.06%, 28.36% and 39.50%, respectively; furthermore, the application of coated urea could slow down the release process of nitrogen fertilizer in soil to make sure enough nitrogen release in the later maize growth period; and after the heading stage, the content of soil alkaline hydrolyze nitrogen of treatment 3, 4, 5 was 40.33%, 66.64% and 53.89% higher than that of the control treatment (bare urea), meanwhile, the application of slow-release coated urea could also significantly improve the grain yield of maize; treatment 4 (2# coated urea) had the best yieldincreasing effect, under which the yield increased by 26.87% compared with that of the control treatment; the nitrogen partial factor productivity, nitrogen agronomy efficiency and nitrogen use efficiency increased by 13.13 kg grain/kg N, 6.76 kg grain/kg N and 10.33% , respectively, compared with those of the control treatment.