A quaternary ammonium derivative of konjac glucomannan (KGM) was prepared by a dry process from KGM and 2,3-epoxypropyl trimethylammonium chloride. We determined the optimization of the experimental conditions by studying on the effects of the water amount, alkaline catalyst amount, reaction temperature, and reaction time on the degree of substitution. In addition, the flocculation characteristics of the cationic derivative of KGM were evaluated in a 1.0% kaolin suspension with spectrophotometry via investigation of the influence of the flocculant amount, pH, salt concentration, temperature, and settling time on the flocculation. The results show that the synthesized cationic KGM could potentially be used as a high-performance flocculating agent. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 2368-2374, 2010