The experiments described in this paper investigate anaerobic fermentation for hydrogen production from eleven organic acids using anaerobic activated sludge as inoculums.Hydrogen gas was produced when using citric,malic,lactic,formic,pyruvic,oxalic,and fumaric acid,and the hydrogen potential at 25℃ for those acids is 171.3,117.4,93.5,79.6,75.6,24.6 and 23.7ml/g,respectively.However,no hydrogen was generated when using succinic,butyric,propionatic and acetic acid.According to the hydrogen potential,energy conversion can be calculated and is lower due to an accumulation of butyric,propionatic and acetic acid that cannot be metabolized by hydrogen-producing bacteria.The study also investigates whether or not organic acids can produce hydrogen gas through anaerobic fermentation.The findings indicate the results depend on the free energy change ( △G(°)) of a hydrogen-producing reaction.If the △G(°) is more than O,organic acids cannot produce hydrogen.