[Objective] By adjusting carbon, nitrogen and phosphorus ratio and domestication model, to improve the ability of active sludge synthesis PHB. PCR-DGGE technology was used to study microbial diversity of domesticated flora. [Methods] In A/O alternate cycle SBR, we used sodium acetate as substrate, gradually improve carbon source concentration and limit concentration of nitrogen source, to create nutrition disequilibrium to gradually improve the content of PHB within activated sludge. [Results] When the COD reach 1 200 mg/L and COD/N/P=1 200/9.6/30, activated sludge synthetized PHB concentration reached the maximum of 64.2 wt% of the dry weight of cells. [Conclusion] In the process of domesticated sludge accumulation of PHB gradually increased, Sudan black, Albert staining and transmission electron microscopy images results showed improve carbon concentration and limit the concentration of carbon which domestication way promote the activated sludge accumulation PHB. DGGE was periodically used to identify the community diversity during the course of domestication and culture period. The population of the activated sludge was belonged to Acinetobacter, Bacillus, Bacteroides sp., Chryseobacteria sp. and proteobacteria.