Acetic acid, propionic acid, lactic acid, butyric acid, and a kind of the mixed four were used as carbon sources for Ralstonia eutropha to biosynthesize polyhydroxyalkanoates (PHAs) in this study. Lactic acid was used up the first among the four organic acids, acetic acid, butyric acid and propionic acid subsequently. Furthermore, acetic acid was produced when propionic acid was used as carbon source for the biosynthesis of PHAs by Ralstonia eutropha, and which was never reported before. In the fed-batch culture, the mole rate of HV component of the PHAs were relatively lower than that of the batch culture, however, the maximum yield of dry cell weight (DCW) and PHAs increased.