The study on flocculation in a Couette flocculator showing Taylor vortices and subsequent solid-liquid separation characteristics was conducted experimentally. In this study silica or kaolin suspensions in water were used to investigate flocculation by cationic polymers. In the present experiments the optimum retention time was found to be about 150 seconds. The optimum Taylor number reached a constant value, when the suspension concentration was less than 1g/l. For the suspension concentration of 3-10g/l, the optimum Taylor number decreased with an increase in suspension concentration. With these results a correlation of the optimum Taylor number was obtained as a function of the suspension concentration and the flocculant concentration. The resulting Camp number at optimum conditions was found to sctter in the range of 1.37×10⁴-5.90×10⁴.