Abstract: In this study, we investigated factors affecting the phosphate solubilizing capacity of Aspergillus niger. A strain named A. niger Xj-2 was isolated by single-spore isolation, with phosphate solubilizing capacity of 539.90 mg·L^-1 in liquid medium. The simulated process of fermentation kinetics showed that phosphate concentration reached equilibrium after 4 d cultivation, indicating that the optimal fermentation time was around 4 d. Phosphate solubilization capacity of strain Xj-2 in different phosphorus-source culture media followed the order: calcium phosphate (539.90 mg·L^-1)>zinc phosphate (238.45 mg·L^-1)>ferric phosphate (182.64 mg·L^-1)>phosphate rock power (71.80 mg·L^-1) > aluminum phosphate (24.40 mg·L^-1). We further examined the optimal condition of strain Xj-2 for phosphate solubilization by response surface optimization combined with single factor experiments. Results showed that the influence of various factors on the phosphate solubilizing capacity of strain Xj-2 was in the order: carbon source > microbial density > pH. The maximum phosphate solubilizing capacity (616.81 mg·L^-1) could be achieved under the following condition with 10.00 g·L^-1 glucose, 0.79 g·L^-1 urea, 35 ℃, the initial pH of medium 6.0, 3.8% microbial density and 160 r·min^-1 rotating speed.