The feasibility of applying chitosan, as prepared from the crab chitin, was assessed in this study for the coagulation of colloidal particles. A series of batch flocculation tests with chitosan under different conditions was also conducted. The results indicate that chitosan is a potent coagulant for bentonite suspension. The relationship between the optimum chitosan dosage and the turbidity of the bentonite suspension is presented as a linear correlation. The evidence infers that an adequate range of the coagulant dosage is the primary consideration in determining the removal efficiency for the turbidity of the source water. It also indicates that the coagulation behavior for kaolinite by chitosan is different from that of bentonite, i.e., chitosan fails to form a good aggregate with kaolinite. Turbid water containing particles which show behavior similar to kaolinite apparently need to have some bentonite particles added as coagulant aid, thereby improving the aggregation of the colloid particles with chitosan. Moreover, the effect of pH on the coagulation efficiency of chitosan is insignificant. The evidence infers that charge neutralization is not a major mechanism controlling the formation of flee for chitosan coagulation.