Coupling bio-production of hydrogen and polyhydroxyalkanoates (PHA) from Taihu blue algae through metabolites circulation was investigated. It was found that the pH adjustment, especially basification was more practical and efficient than other methods for the pretreatment of blue algae before anaerobic digestion. On this occasion, SCOD, biogas accumulation and hydrogen content reached 26 mg/gTS, 500 mL and 37.2%, and which were 4.3, 1.3 and 14.4 times of those of the control group, respectively. Secondly, amounts of both butyric acid and hydrogen could be further increased when blue algae was alkali pretreated at pH 13, as the accumulation of butyric acid, acetic acid and hydrogen reached 1.7, 1.4 and 3.8 times compared to those of the control, respectively. Finally, the coupling bio-production of hydrogen and PHA was conducted through pumping organic residues into PHA fermenter from anaerobic digester. Remarkably, it was found that the larger the pumping rate of carbon and nitrogen sources supply, the higher the yield of DCW and PHA could be expected by Bacillus cereus. (C) 2010 Published by Elsevier Ltd.