In this manuscript, some analyses including differential chemical oxygen demand (COD), gas production, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) in addition to the properties of degradable process about polyacrylate and polyacrylate/ZnO were studied in order to evaluate the influence of nano-ZnO on the biodegradation of polyacrylate in two different activated sludge systems. The results indicated that nano-ZnO will improve the biodegradability of (C5H8O2)4-(C7H12O2)6 under aerobic condition, while it can dramatically worsen the biodegradability of (C5H8O2)4-(C7H12O2)6 under anaerobic condition. The FTIR results show that the influence of nano-ZnO on the biodegradability of polyacrylate mainly depends on the mode of ZnO (molecular or ion). Nano-ZnO particles in aerobic systems were stable and subsisted together with polyacrylate adsorbed on the surface of activated sludge, which could improve the biodeteriodation and depolymerisation of polyacrylate. However, nano-ZnO particles in aerobic system could dissociate into Zn2+ and O2-. This phenomenon replaces the intermediate products on the surface of anaerobic sludge is toxic for bacteria in anaerobic sludge, which inhibits the activity of methane in anaerobic sludges. [ABSTRACT FROM AUTHOR]