In this paper, the natural organic polymer flocculants (RHF) is prepared by cationic modified rice husk, a kind of agricultural waste. Effects of flocculation are discussed between RHF and cationic polyacrylamide (CPAM), polymeric aluminum ferric (PAFC) with different proportion, respectively. The results indicate that RHF, with a better salt tolerance, can remove contamination in water effectively and improve water quality significantly. Besides, RHF and CPAM complex system results in an excellent synergistic effect and enables dredged sludge to flocculate dewatering instantly with promotion of water quality.