Abstract: Four strains of thermo-stable inorganic phosphorus-solubilizing microorganisms (X₁, X₂, X₃, X₄) and two strains of cellulose-degrading microorganisms (X₅, X₆), screened and domesticated in previous experiments, were selected and mixed at different ratios according to uniform experimental design methods, and then cultured in fermentation broth to enhance the conversion efficiency of insoluble phosphorus and degrading rate of composting materials during the compost process. The ratio of each microorganism in the complex bacteria was optimized by analysis of the indexes of solubilizing insoluble phosphorus capabilities using uniform Design Software and Data Processing System (DPS). The results indicated that the optimum ratio of the complex bacteria was: φ(X₁)=13.66%, φ(X₂)=11.36%, φ(X₃)=11.41%, φ(X₄)=13.61%, φ(X₅)=10.62%, and φ(X₆)=39.34%. The phosphorus-solubilizing capability of the optimized complex bacteria was investigated, and the measured total mean value of solubilized-phosphorus was 230.12 mg/L, which was in accordance with the theoretical value of 228.75 mg/L by regression. The complex bacteria combination was also inoculated into cellulose fermentation broth, and the CMCase activity attained as high as 39.76 U after 168 hours’ culture.