Abstract: The nitrification inhibition of dicyandiamide on urea in the red soil of different textures was studied.The results show that the hydrolyzation rate of urea in the loam soil and the clay soil is quicker than that in the sandy loam soil,and dicyandiamide slows down the nitrification of urea in the loam soil and clay soil but improves it in the sandy soil.The transformation of urea in the sandy soil by adding or without adding dicyandiamide needs 49 days.It requires 35 days in the clay while it is prolonged for 14 days after adding dicyandiamide.However the nitrification time of urea in the loam needs further research.