The granulation of PCP degrading anaerobic sludge in two improved UASB reactors under co-existence of two types of industrial wastewater and PCP were studied. It was found that the granulation of PCP degrading anaerobic sludge could be divided into three stages, i.e. sludge acclimation, granular pre-formation and granular maturation. The changes in biomass, sludge bioactivity, population and ecological distribution of three group bacteria involved in anaerobic digestion during the course of granulation were also examined. Anaerobic granules from two reactors showed high dechlorination activity at meta, otho and para position. Rod-shaped and filamentous shaped Methanosaeta-like spp. were found in anaerobic granules. Results of electron microscopy revealed the presence of synthophic microcolonies and non-layed microstructure in PCP-degrading granules. The types of industrial wastewater used as co-substrate had affected the course of sludge granulation, dechlorinating activity and pre-dominant methanogens in PCP-degrading anaerobic granules.