Preparation of konjac glucomannan-grafted poly(trimethyl allyl ammonium chloride) (KGM-g-PTMAAC) was carried out using KGM as polysaccharide matrix and TMAAC as cationic comonomer to develop biodegradable flocculants. The structure of KGM-g-PTMAAC was characterized by FTIR, C-13 solid-state NMR, elemental analysis (EA) and SEM. Thermal properties of KGM-g-PTMAAC were studied by thermal gravimetric (TG) analysis. In addition, flocculation properties of KGM-g-PTMAAC were investigated in a kaolin suspension. The results of the FTIR, NMR, and EA showed that the cationic moiety containing quaternary ammonium has been introduced in the backbone of KGM. SEM images indicated that the surface of KGM-g-PTMAAC was rougher than that of KGM. TG results indicated that the thermal stability of KGM-g-PTMAAC was different to that of KGM. The obtained products had a good biodegradable performance. Moreover, the results of the flocculation test showed that KGM-g-PTMAAC could be potentially used as a good flocculating agent.