The study on changes in microbial properties as affected by addition of carbons of different sources and N concentration at the fertisphere is of great significance to understanding of effects of carbons of different sources regulating nitrogen transformation in fertispheres different in concentration and improving nitrogen use efficiency. Samples of paddy soils typical of the subtropical region of China were collected and treated with ammonium sulphate at different rates and carbons of different sources, separately to simulate different fertispheric nitrogen concentrations. The treated soil samples were then incubated in lab and analyzed for changes in biomass carbon and nitrogen of the soil microbes, nitrogen mineralization and functions of the microbial communities. It was found that after 7 or 35 days of incubation, in treatments high in N application rate, addition of glucose, cellulose and lignin separately increased microbial biomass carbon by 5.0%~126.8%, 17.5%~210.9% and 14.7%~210.0%, respectively, and microbial biomass nitrogen by -15.4%~109.3%, 32.0%~173.1% and -34.2%~194.8%, respectively, and in treatments, medium or low in N application rate addition of any of the three types of carbon also stimulated somewhat increase of microbial biomass carbon and nitrogen. Regardless of fertispheric N concentrations, the treatments with glucose were the highest in CO₂ emission, those with cellulose came the next and those with lignin the last. BIOLOG analysis showed that AWCD value and Shannon, Simpson and McIntosh indices were all quite low in treatments either high or medium in N application rate, and they were increased after addition of carbon. In treatments with carbon added alone or treatments with carbon and N fertilizer added at a normal rate, AWCD value, Shannon, Simpson and McIntosh indices were all relatively high. In treatments high in fertispheric N concentration, addition of any of the three, glucose, cellulose or lignin increased soil microbial activity. So, in the current condition of using large volumes of inorganic N fertilizer, it is advisable to use organic manual in addition, which helps reduce the risk of nitrogen loss.