In this study, paddy soil samples in latitude sequence were collected from southern China. Soil organic nitrogen composition was identified by using the modified Bremner method. Various soil organic nitrogen forms including amino-acid N, amino-sugar N, ammonium N and unknown hydrolysable N were determined. Results showed that the contents of soil total N and various N forms in paddy soils were not related to the latitude which were considered to be attributed to the interactions of field management and environment. However, the proportions of various N to total N were linear to the latitude, the determination coefficient values were 0.556 6, 0.729 3, 0.803 6, 0.897 5 and 0.411 3 for hydrolysable N, non-hydrolysable N, amino-sugar N, unknown hydrolysable N and ammonium N, respectively. Overall, the field management exerted a great influence on the contents of soil total nitrogen and its components. The environmental condition played a key role in soil nitrogen composition.