【Objective】soil nitrification potential (NP) and its main influencing factors in fluvo-aquic soils were studied based on a long-term fluvo-aquic soil fertilization experiment in Zhengzhou, Henan Province. 【Method】Three tracts of farmlands of fluvo-aquic soil different in fertility level, i.e. High (applied with chemical fertility plus organic manure); Moderate ( applied with balanced chemical fertilizers); and Low (applied with no fertilizer or no N fertilizer), were selected for soil sampling for analysis of total N (TN), ammonium nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃^--N), microbial biomass C (MBC) and microbial biomass N (MBN). And stepwise regression analysis, path analysis and variance decomposition analysis (VDA) were performed to define main influencing factors in fluvo-aquic soil relative to soil fertility and quantify contribution of each factor to NP. 【Result】Results show that NP in the fluvo-aquic soils varied in the range of 0.3 mg•kg^-1•h^-1~1.1 mg•kg^-1•h^-1, and differed significantly between the soils. It was 7.9% higher in the soil high in fertility than in the soil moderate in fertility, and 162.5% higher in the soil moderate in fertility than in the soil low in fertility. Among all the soil fertility indices, MBC, NO₃^--N, TN and MBN were found to be the main influencing factors of soil NP. MBC, NO₃^--N and MBN affected NP directly, while TN did more indirectly. The contribution rate of microbial biomass (MBC and MBN), NO₃^--N and TN to NP variation is worked out to be 24.3%, 18.9% and 13.7%, respectively. The contribution of four main influencing factors’ interaction effects to the variation of soil nitrification potential has reached to 52.8%, while the total contribution of each variant and its interaction effects amounted to 92.9%. Therefore, it can be concluded that nitrification is much stronger in soils of high fertility than in soils low and moderate in fertility. 【Conclusion】As result of strong nitrification, ammonium nitrogen is nitrified into nitrate nitrogen, which is readily accumulated and/or leached. It is, therefore, essential to regulate soil water and nutrient regimes to a proper level so as to reduce soil nitrification intensity and eventually achieve the target of constructing a nitrogen nutrient pool and reducing nitrogen loss in fluvo-aquic soils.