In the biofilm wastewater treatment process, the start-up period of biofilm process is affected by the biofilm formation on the surface of carriers. Controlling surface charge property of carriers could accelerate the biofilm formation. The surface of conventional biofilm carriers, such as polyethylene (PE), polypropylene (PP) and high-density polyethylene (HDPE) is negatively charged, as is the surface of bacterial cells of activated sludge, which could lead to electrostatic repulsion between the biofilm carriers and the bacteria. Herein, the conventional high-density polyethylene (HDPE) carriers were modified by two kinds of positively charged polymers with different charge strength, which were noted as polyquaternium-10 (PQAS-10) and cationicpolyacrylamides (CPAM), respectively, to accelerate the startup of biofilm-based wastewater treatment process. The results showed that the positive Zeta potential was measured on the surface of modified carriers, whereas the surface Zeta potential of unmodified carriers was negative. It indicated that the modified carriers carried positive charge. Furthermore, the positive charge on the modified PQAS-10 carriers was higher than that on the modified CPAM carriers. The reactor with modified PQAS-10 carriers achieved shorter reactor start-up time and higher attached biomass compared to that with unmodified carriers and modified CPAM carriers. As a result, the removal efficiencies of COD, NH4+-N and TN in the reactor with the modified carriers were higher than that with the unmodified carriers. These findings demonstrated that the success of electrophilic modification on the surface of carriers was expected to accelerate the startup of biofilm-based reactors and improve the reactor performance in the practical application. (C) 2017 Elsevier B.V. All rights reserved.