Azospirillum brasilense and Pseudomonas fluorescens are well-known plant growth promoting rhizobacteria.  However, the effects of A. brasilense and P. fluorescens on the N cycles in the paddy field and rice plant growth are little known.  This study investigated whether and how A. brasilense and P. fluorescens contribute to the N transformations and N supply capacities in the rhizosphere, and clarified the effects of A. brasilense and P. fluorescens on the N application rate in rice cultivation.  Inoculations with A. brasilense and P. fluorescens coupled with N application rate trials were conducted in the paddy field in 2016 and 2017.  The inoculations of rice seedlings included four treatments: sterile saline solution (M₀), A. brasilense (M_b), P. fluorescens (M_p), and co-inoculation with a mixture of A. brasilense and P. fluorescens (M_bp).  The N application rate included four levels: 0 kg N ha^–1 (N₀), 90 kg N ha^–1 (N₉₀), 180 kg N ha^–1 (N₁₈₀), and 270 kg N ha^–1 (N₂₇₀).  The results indicated that the M_bp and M_p treatments significantly enhanced the ammonification activities in the rhizosphere compared with the M₀ treatment, especially for higher N applications, while the M_bp and M_b treatments greatly enhanced the nitrogenase activities in the rhizosphere compared with the M₀ treatments, especially for lower N applications.  Azospirillum brasilense and P. fluorescens did not participate in the nitrification processes or the denitrification processes in the soil.  The soil respiration rate and microbial biomass N were greatly affected by the interactions between the rhizobacteria inoculations and the N fertilizer applications.  In the M_bp treatment, N supply capacities and rice grain yields showed no significant differences among the N₉₀, N₁₈₀, and N₂₇₀ applications.  The N application rate in the study region can be reduced to 90 kg N ha^–1 for  rice seedlings co-inoculated with a mixture of A. brasilense and P. fluorescens.