Novel cellulose based flocculants C-g-P (DMC) with various chain architectures are synthesized through a situ graft copolymerization. The cationic ammonium chloride group (DMC) is grafted onto cellulose by two separate inverse emulsion polymerization with γ-methacrylox-ypropyl trimethoxy silane (KH-570) and double bond addition reactions, which is a new and simple method to employ KH-570 as a bridge for the connection of cellulose matrix and DMC group. The effects of pH, flocculant dose, standing time on turbidity of kaolin suspensions and particle sizes have been studied systematically. In addition, the response surface methodology (RSM) study confirms that PAC and C-g-P (DMC) have synergy in turbidity removal with a higher removal efficiency of 98.32％. Moreover, C-g-P (DMC) 1 has higher removal efficiency with 96.5％at a low dosage of 0.6 mg L-1 and better floc properties than C-g-P (DMC) 2 and C-g-P (DMC) 3, suggesting that the length and quantity of cationic branch chains play a crucial role in Kaolin flocculation due to their dramatically enhanced bridging effects.