The production of Poly(hydroxyalkanoate) (PHA) from organic wastewater by a composite anaerobic acidification-fermentation system was developed and the degree of acidification and products distribution were examined. The production of PHA from acidified wastewater was examined in both batch and fed-batch fermentation. Butyric acid was the most suitable acid for Alcaligenes eutrophus growth and PHA accumulation. Over 99% acidification and favourable organic acid distribution in the effluent of an acidogenic UASB was obtained at 40 degrees C and pH 5.7. The amount of PHA accumulated in A. eutrophus on the acidified and concentrated wastewater in fed-batch fermentation was 10 g/l, accounting for 63.3% of cell mass.