Abstract: A pot experiment was conducted by using ~(15)N isotope tracer in studying carefully the fate of two kinds of N fertilizers——urea and ammonium nitrate in two types of soils in central China——yellow brown soil and red yellow soil, and the influence of urease inhibitor. The volatilization and eluviation of the two kinds of N fertilizers after applying to wheat growing soils were elucidated. The result is put forward for the first time that the loss of N caesed by volatilization is more than eluviation. The effect of urease inhibitor in raising N-fertilizer efficiency and reducing loss by volatilization of urea was ascertained.