In order to overcome the disadvantages of the anaerobic reactor such as slow growth and long start-up, the flocculent anaerobic sludge was embedded and used as the seed sludge in the anaerobic treatment of PTA wastewater with the objective of keeping biomass in the reactor. The start-up characteristics of the UASB reactor were investigated. During the 136 days' running, COD removal rate of PTA wastewater achieved 75%-85% at the volumetric loading rate (COD) of 3 kg x (m3 x d)(-1) and the hydraulic retention time (HRT) of 3-4 day. The anaerobic system had good stability and biomass retaining ability. On the other hand, variations of EPS, SEM observation and methanogens DNA in sludge granules verified the growth of immobilized bacteria in both quantity and microorganism morphology, although mass transfer through the immobilization media was to some degree limited.