With the promotion of the polymer oil-displacing technology in China, polyacrylamide (PAM) are widely used in the exploitation of oil. Biodegradation of partially hydrolyzed polyacrylamide (HPAM) may be an efficient way to treat oilfield sewage, because part of the amidogen and carbon of the HPAM could be utilized as the source of nitrogen and carbon nutrition for the growth of microorganism in anaerobic environment. The HPAM wastewater was treated by combined Fenton oxidation and anaerobic biological processes in this paper. The optimum dosages of Fenton pretreatment were determined to be 5.3 mmol L-1 H2O2, 1.44 mmol L-1 Fe2+, pH 3.0 and 30 degrees C. The influence of parameters on CODCr and HPAM removals followed a decreasing order of [H2O2] > [Fe2+] > pH > temperature. The pretreated wastewater was further treated by an anaerobic reactor (ABR). Through the combined processes, the maximum CODCr and HPAM removal ratios were 94.61% and 91.06%, respectively. Among the removal ratio, the respective contribution ratios of Fenton oxidation were 72.92% and 69.44%. According to IR analysis, microorganisms could degrade HPAM and utilize part of the amidogen and carbon for their growth. SEM analysis showed that macromolecular HPAM was degraded into micromolecular compound. The processes were proved to be a suitable technique for dealing with high concentration HPAM-containing wastewater. (C) 2015 Elsevier B.V. All rights reserved.