Using various organics as electron donor, (GuIn)(0.2)Zn1.6S2 microsphere solid solution prepared via hydrothermal method as photocatalyst, hydrogen production by anaerobic photocatalytic reforming organics were researched. The photocatalytic hydrogen production activity was notably enhanced in the presence of the organic electron donors. Formic acid was found to be the most efficient sacrificial agent among methanol, glucose, triethanolamine and formic acid. The effects of initial formic acid concentration on hydrogen generation were investigated. When the initial formic acid concentration was 10 vol%, the photocatalytic activity reached the highest. The average activity in initial 10 h can amount to 144 mu mol h(-1). The possible mechanism of photocatalytic reaction for hydrogen production with simultaneous formic acid degradation was discussed preliminary. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.