Soil dissolved organic carbon (DOC) is an important fraction in the global carbon cycle and is critical to soil biogeochemical processes related to soil fertility and climate change. Soil bacteria play an important role in controlling soil DOC dynamics. To determine effects of phosphorus (P) fertilization rate on paddy field soil mineralization of the soil organic carbon, DOC structural complexity and bacterial community structures, a stationary field experiment, designed to have four P application rates, i.e. 0, 30, 60 and 90 kg hm^-2a^-1 of superphosphate, was carried out in a paddy field, and lab analysis was performed with the 3D EEMs and 454 pyrosequencing techniques. Results show that higher P application rate raised the content of soil readily available phosphorus (Olsen-P), thus increasing the content of soil DOC, and DOC mineralization rate and accumulative mineralization as well. Analysis with the 3D EEMs demonstrates that P input increased fluorescence index and β/α index of the DOC by 1%~10% and 3%-21%, respectively, but decreased its humification index, which were significantly related to soil biochemical properties (Olsen-P, DOC and β-glucosidase). The results also indicate that P application increased the content of Olsen P, stimulated formation of microbe-derived DOC and meanwhile decreased the aromatization degree, molecular weight and humification degree of the DOC, thus improving the biodegradability of the DOC. P input also increased the abundance and diversity of microbial communities, and in particular, induced growth of a variety of carbon-degrading bacteria , thus speeding up degradation of complicated organic carbon and oxidation of methane. Besides, principal component analysis shows that the effect of P fertilization on mineralization of SOC and diversity of bacterial communities was the most significant when P 30～60 kg hm^-2a^-1 was applied. It is, therefore, assumed that a proper rate of P applied may significantly stimulate the activity of C-degradation-related microbes, and hence improve the biodegradability of DOC, accelerate mineralization of the soil organic carbon and promote the cycling of soil organic carbon in paddy field.