Effect of carbon source (glucose, pyruvate, yeast extract) and electron donor (H2) on anaerobic degradation of pentachlorophenol (PCP) was investigated. Differences of bacterial community in the anaerobic systems were also detected by terminal restriction fragment length polymorphism technique (T-RFLP). Compared with carbon-free system, the supplementation of different carbon sources and H2 may greatly enhance the degradation of PCP. The analysis of T-RFLP showed that bacterial community structures were different under different treatment conditions. It was speculated that some microorganisms phylogenetically affiliated with the genus Clostridium, Frankia and Desulfitobacterium existed in the PCP- degradating systems.