Use of water-soluble and -insoluble starch grafting acrylamide/sodium allylsulfonated copolymers as flocculants to flocculate the clay suspension was investigated. The composition of acrylamide (AM), sodium allylsulfonated (SAS), and starch (St) repeating units in the water-soluble and -insoluble starch-grafted copolymer is about 0.718, 0.022, and 0.260 and 0.439, 0.014, and 0.547, respectively. For the water-soluble starch-grafted copolymer, the fast initial A(r) decreasing rate and the lowest final A(r) value occur at pH 2, 80 mg/L water-soluble starch-grafted copolymer and 100 mg/L clay suspension. As the suspension contains 1000 mg/L Na+ ion, the flocculating capability would be increased. For the water-insoluble starch-grafted copolymer, the initial A(r) decreasing rate and the final A(r) value are 1.6 times and 0.4 times, respectively, that of the water-soluble starch-grafted copolymer at the same test suspension.