This study aimed at investigating the desalination performance of ion exchange membranes (IEMs) treating polymer flooding wastewater and influence of partially hydrolyzed polyacrylamide (HPAM) molecular weights (MWs) on membrane fouling. Adsorption of HPAM on IEMs and molecular weight distributions (MWDs) of HPAM in chemical cleaning solutions were analyzed to study IEM fouling characteristics. Experimental results indicated that HPAM affected the desalination performance most significantly compared to oil. Moreover, cation exchange membranes (CEMs) were easier to be polluted by HPAM with lower MWs while anion exchange membranes (AEMs) were easier to be polluted by HPAM with higher MWs. It was also found that the heterogeneous IEM fouling caused by HPAM was more severe than the homogeneous IEM. Furthermore, CLSM, FTIR, electrostatic interaction and interface thermodynamics analysis indicated that HPAM caused membrane fouling and the main mechanism was electrostatic interaction. (C) 2016 Elsevier B.V. All rights reserved.