The copolymerization reaction between gomuti starch and acrylamide was initiated using (NH4)2S2O8 as initiator under microwaves heating at 60~80 . The analysis of the Fourier transform-infrared spectroscopy and Scanning electron microscopy showed that the product is gomuti-graft-polyacrylamide. The productivity of graft copolymer and the conversion rate of acrylamide vary with the weight ratio of acrylamide and gomuti starch (AM/GOM). They reach maximum value when AM/GOM≈2.5. The flocculating test showed that in water of yellow mud , the turbidity removal rate of gomuti-graft-polyacrylamide is better than that of polyacrylamide.