The 23 soil samples including the 6 types of managed soils were collected different regions in Shanxi Province for this research project The change of nitrate nitrogen accumulation with time was detemvned during the process of nitrification. The equation, dN/dt=bN(B-N)/B(N is the amount of NO₃^-N accumulation, t is time of incubation, and B is the asymptotic value of NO₃^-N, depending on the amount of NH₄-N added to the soil), was used to represent the accumulation of nitrate nitrogen with time. The maximal rate of nitrification (K_mx) and the delayed period (t_d) were derived from the equation and used to characterize quantitatively the nitrification process in various soil samples. The K_mx and t_d of surface soil samples were from 2.7 to 16.58 mg/kg·d and from 1.3-3.5d, respectively. The K_mx decreased and t_d increased with soil depth. Some soil properties affected the rate parameters.