Abstract: Based on a 16-year long-term fertilization experiment with fixed site on paddy soil in Shenyang, Liaohe plain, the effect of long-term fertilization practices on nitrogen mineralization characteristic of paddy soil was studied. Results showed the nitrogen mineralization potential and mineralized rate was affected significantly by different long-term fertilization practices. Compared with control (no chemical nitrogen application), single application of nitrogen fertilizer could decrease nitrogen mineralization potential but increase mineralization rate. Applying nitrogen fertilizer and manure could increase nitrogen mineralization potential very significantly and decrease mineralization rate. Applying chemical nitrogen fertilizer and manure and inoculating “Azolla” for 7-years after transplanting rice seedlings could decrease nitrogen mineralization potential and increase mineralization rate.