In this paper the relationship between the parameters of the regression equation of nitrogen fertilizer efficiency for early rice plant,ŷ=a+bx+cx², and those of the equation of accumulated mineralied nitrogen curve,ŷ=Kxⁿ, is discussed.Experimental results showed that there were three couples of curve derived from the equtions which revealed similar trends in three grougs of paddy soil. Results also showed that a significant correlation existed between the garameters "K" and "a", as well as between the amount of soil nitrogen mineralized through eight weeks incubation and the amount of maximum nitrogen application described by "-b/2c".It is suggested that the characteristics of N response curve and the maximum amount of N application for early rice could be predicted through the determination of nitrogen mineralization by incubalion method.