Phosphorus (P) is one of the most important essential elements for plant growth and function. However, both the concentration and the availability of P are very low in most soils. The chemical P supplemented through fertilization is rapidly adsorbed by soil minerals or transformed by soil microbial organisms resulting in a 10%-20% of P use efficiency. Studies have found that Azotobacter sp., which can fix nitrogen from the atmosphere to contribute plant nitrogen nutrition, also has the capacity to mobilize soil P for plant use. As a result, the improvement of plant P use efficiency through some specific soil Azotobacter to mobilize soil P has attracted much attention around the whole world. However, less information is available to illustrate the mechanisms how Azotobacter sp. could directly mobilize P from the soil. Five strains of Azotobacter sp., which isolated from a gray brown purple soil in Chongqing, southern China and coded as N 01、N 02、N 03、N 04 and N 05, respectively, were grown a liquid medium to study their capacity to mobilize soil phosphorus (P). The medium contained 1L H₂O, 10 g mannitol, 0.2 g KCl, 0.2 g MgSO₄·7H₂O, 0.2 g NaCl, 0.2 g CaSO₄·7H₂O and 5.0 g CaCO₃. Compared to the non-Azotobacter control, concentrations of proton in the liquid media under all five Azotobacter treatments were increased by 58 times leading a significant pH decrease after 7 days of incubation. All Azotobacter strains exuded oxalic acid and malic acid, but varied their capacity to exude succinic acid, formic acid, acetic acid, citric acid and lactic acid. Total P in the liquid medium was significantly higher whilst inorganic P was significantly lower in the soil in the Azotobacter treatments than in the non-Azotobacter treatment. pH in the liquid medium positively correlated with soil total inorganic P (r=0.959^{* *}, n =6), but negative correlated correlations with both inorganic P and total phosphorus in the liquid medium (r=-0.850^* or -0.918^{* *},n =6). Meanwhile, soil Ca-P was significantly reduced by all Azotobacter treatments, while Al-P, Fe-P and occluded P were decreased depending on the Azotobacter strain used in this study. On one hand, our results suggest that the capacity of exuding organic acids and hence mobilizing soil P by Azotobacter may be species dependent. On the other hand, our results showed that the pH decrease in the liquid medium might be one of the most important mechanisms to mobilize soil Ca-P and/or Mg-P while the organic acids might contribute directly in the mobilization of soil P through the complexion and acidic solution. As a result, our results demonstrated an alternative pathway to enhance plant P nutrition through Azotobacter and could offer a potential effective practice to increase crop productivity by intercropping or growing cereal crops with legumes, in which the latter could not only provide nitrogen, but also P, to meet the growth requirements of both nitrogen and P for the cereal crops. Nevertheless, more research on the capacity of Azotobacter to mobilze soil P and associated nitrogen and P benefits to its host plants and neighbouring plants are further required.