Abstract: In order to unify the measurement conditions of soil nitrification activities and increase the accuracy of results, the optimum culture conditions of suspension method for measuring soil nitrification activities were improved: the pH of the reaction system was 7.5, the substrate concentration of NH4+-N was 100 mg/L, culture temperature was 30℃, culture time was 5 h, and soil nitrification activities was measured after air-dried soil sample pre-cultured for 72 h. The study also aimed at the deficiency of preparation method of NO₃^--N, and discussed the method of measuring soil nitrification activities by the preparation method of NO₂^-- N. The method was adding 1 mol/L sodium chlorate 0.2 mL to the reaction system for effective inhibition of NO₂^- to NO₃^- oxidation. By comparing different methods, the preparation method of NO₂^--N was the best method of measuring soil nitrification activities.