The ultrasonic heterogeneous copolymerization of poly (ethylene oxide) (PEO) in its aqueous solution with hexyl methacrylate (HMA) was studied. The experimental results show that the macroradicals praduced in the ultrasenic degradation of PEO can initiate the polymerization of HMA. The copolymer (PEO-HMA) thus formed will be degraded further as the irradiation goes through. The structure of the copolymer was idontified by IR