The spatial characteristics of biological nitrogen fixation (BNF) of rice paddy soils in Yixing city was studied using the acetylene reduction method and geostatistics method. Soil samples were collected systemically with a grid of 2 km×2 km. Results showed that BNF rate ranged from 0.75 to 46.85 g/m² with an average of 8.04 g/m² . The raw data was logarithmically transformed to meet a normal distribution and then an optimized Kriging method was employed to describe the spatial distribution of BNF. BNF showed a belt distribution in the study region. The high value of BNF occurred in the southwest and southeast areas while the low value in northwest and northeast areas of the study region. The variation coefficient and nugget value showed a medium spatial variation of the BNF. Generally, BNF of paddy soils was influenced simultaneously by the artificial management and natural condition.