Abstract: Soil mineralization culture experiments by Warning's method were conducted to investigate the mineralization characteristics of soil organic N in tobacco field by using soils from several typical tobacco fields in Hunan province. The results showed that, for all of the soil samples, the mineralization rate of soil organic N was fast in early stage and slow in late stage. Mineralized nitrogen accumulation, mineralization rate, and mineralization potential were different among the three typical tobacco fields, e.g., middle Hunan>southern Hunan>western Hunan. The regression analysis showed that active organic carbon, total nitrogen, total organic matter, and soil humus, from strong to weak, were most influential to soil mineralization nitrogen content. Overall, active organic carbon had the closest relationship with mineralized nitrogen accumulation and was the major origin of the mineralization .