Abstract: To obtain high density bacterial fertilizer of phosphate-solubilizing bacteria, culture conditions for a strain of phosphate-solubilizing bacteria Bacillus megaterium isolated from soil were optimized, and OD600 of the broth was used as a standard to judge the number of viable cells. Firstly, single factor experiments were used to research the effects of different factors of inoculation amount, medium volume, culture temperature, initial pH, incubation time, and rotate speed on submerged fermentation and the best values of single factors were obtained. Then orthogonal experiment of L9(34) was used to optimize the optimal culture conditions. After that, growth curve of the strain was described. The results showed that the optimal culture conditions were: temperature of 30℃, initial pH of 8.0, medium volume of 20 mL/250 mL flask, inoculation amount of 3%, rotate speed of 250 r/min, and incubation time of 22 h; under the optimal culture conditions, the number of viable cells of Bacillus megaterium reached above 3.2×109 cfu/mL. The period between 2 hours to 8 hours after inoculation was logarithmic phase for cell growth, then cell growth was in the stable stage, and after 22 hours, decline phase started. The results could provide basic data for production of phosphate-solubilizing bacterial fertilizer for agricultural application.