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The priming effect of nitrogen fertilizer on soil nitrogen was studied by using waterlogged incubation method. The results showed that ammonium nitrogen of fertilizer and being released in the incubation could be fixed by clay mineral inevitably, in order to obtain the reliable results, this form of nitrogen must be considered in determining the priming effect. On the other hand, the priming effects of nitrogen fertilizer were different with the type of organic materials in soil, in general, the C/N ratio of organic material being low, the nitrogen fertilizer had positive priming effect, on the contrary, the nitrogen fertilizer had negative priming effect.