In this paper, a series of PANI-CdS (PANI is the abbreviation of Polyaniline) composites were synthesized by changing the mass of PANI (molar ratio of PANI and CdS : 0.5, 0.7, 1, 1.5, 2). The PANI-CdS composites were characterized by XRD patterns, IR spectra and elemental analysis. The activities of as-prepared composites were also tested with regard to hydrogen evolution. It was found that PANI-CdS composites showed good activity for hydrogen evolution. With increment of PANI, the activity for hydrogen evolution of PANI-CdS reduced. But compared with pure CdS, PANI-CdS had a much higher activity for hydrogen evolution. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.