In this study, the flocculating properties of chitosan-graft-polyacrylamide (PAM) copolymer flocculants have been investigated in pilot scale, and the raw water from Zhenjiang part of Yangtse river in China was used as simulated waste water. The influences of dose, mechanical mixing rate, and sedimentation time to the flocculating effects have been investigated in different seasons: summer and winter, respectively. The optimal experimental conditions have been studied by orthogonal test. In addition, the structure effects of the flocculants: the grafting ratio, on the flocculating properties have been also investigated in pilot scale, which results were fully consistent to those from the beaker experiment in laboratory scale using kaolin suspension as simulated waste water. Compared to poly ferric sulfate, current used flocculants in Jinxi Water Factory, chitosan-g-PAM copolymer flocculants showed better flocculating properties, which was ascribed to the cooperative effects of the charge neutralization and bridging flocculating mechanisms of polymer flocculants. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 2016-2024, 2010