In this study, the purpose was to understand the effect of the interaction between bacillus ZJMP5 and phosphate fertilizer on the root development and yield of adzuki bean. The pot experiment was conducted in 2016 and 2017 using ‘Jinhong No.5’ adzuki bean (Phaseolus angularis Linn.). The experiment consisted of two factors: phosphate fertilizer and bacillus ZJMP5. Three levels of P₂O₅ ［50 (P₁), 100 (P₂), 200 (P₃) mg·kg^-1］ and four levels of bacillus ZJMP5 ［10⁶ (A₁), 10⁷ (A₂), 10⁸ (A₃), 10⁹ (A₄) cfu·mL^-1］ were designed. Moreover, no P fertilizer and bacillus ZJMP5 was designed as control, and there were 13 treatments in our study. The root morphology, physiological characteristics and yield of red adzuki bean seedlings under different interaction levels of P fertilizer and bacillus ZJMP5 were analyzed. The results showed that: (1) the bacillus ZJMP5 and compound phosphate fertilizer treatments (phosphorus bacteria interactions) were significantly increased adzuki bean seedling taproot length, root area, root volume (P < 0.05). The seedling root length and root cap ratio are the highest under P₁A₃ treatment, 83.1% and 50.9%, respectively, compared with the CK significantly increased. The root area and root volume were the highest under P₂A₂ treatment, 69.7% and 54.2%, respectively, compared with the CK significantly increased. (2) The root SOD and POD activities, root activity and soluble protein content in the roots of rhododendrons seedlings were significantly increased by the interaction of each phosphorus bacteria, and all reached the peak value at P₂A₂ treatment, while MDA and soluble sugar contents in the roots of rhododendrons seedlings were significantly reduced, and all reached the minimum value at P₂A₂ treatment. (3) The P content of rhododendrons seedlings was significantly increased and the acid phosphatase activity of the roots was significantly decreased by the interaction of phosphorus bacteria. With the increase of phosphorus application, P content of plants increased gradually, and acid phosphatase activity of roots decreased gradually. As the concentration of bacterial solution increased, the P content of plant and the activity of acid phosphatase in root system both first increased and then decreased, and were the highest at the concentration of A₂. (4) With the increase of phosphorus application level or concentration of bacterial solution, the 100grain weight and grain yield of adzuki bean increased first and then decreased. In addition, under the P₂A₂ treatment combination, the yield increase was the best, which increased by 141.60% and 210.40%, respectively, compared with the control group. It was found that bacillus ZJMP5 could improve the grain yield of adzuki bean by changing root configuration, increasing root activity and improving root physiological function, and the optimal effect of growth promotion and yield increase could be achieved under the interaction of 100 mg·kg^-1 phosphorus application and 10⁷ cfu·mL^-1 bacterial liquid concentration.