Abstract: Under hydroponic conditions, the phosphate solubilizing capacity of the four tested strains(Bmp5, Bmp6, Bmp7 and Fmp9) in dissolving five different poorly soluble phosphates were studied with two strains(Pesudomonas fluorescens As1.867 and Bacillus megatherium As1.223) as control. A co-culture experiment with these four strains, compared to the single cultivation, was conducted in order to reveal their mutual influences on the phosphate solubilizing activity. The results indicated that these single strains exhibited higher solubilizing abilities in Ca₃(PO₄)₂, AlPO₄·2H₂O and CaHPO₄·2H₂O than in FePO₄·2H₂O and lecithin. As an example, when using Ca₃(PO₄)₂ as the sole phosphate source, the amount of the phosphate solubilizing capacity of Fmp9 was 92% and 48% higher than those of the references As1.867 and As1.223, respectively. As1.223 showed the maximum solubilization in AlPO₄·2H₂O. In all four tested strains, Bmp6 was the dominant strain in solubilizing CaHPO₄·2H₂O, and its phosphate solubilization capacity could be as high as 785.51 mg/L. The best phosphate sources for Bmp5, Bmp6, Bmp7 and Fmp9 were lecithin, CaHPO₄·2H₂O, AlPO₄·2H₂O and Ca₃(PO₄)₂. Furthermore, the study of the hydroponic co-culture of the four strains showed that the combinations of Bmp5+Fmp9 and Bmp6+Fmp9 were the preferable combinations in terms of phosphate solubilizing activities. The phosphate solubilizing microorganisms in this experiment have been used to the biological compound fertilizer and the pot experiment showed a satisfactory result. This research can provide referencesfor biological compound fertilizer.