Abstract: The compatibility of poly ( ethylene oxide) (PEO)/Polyacrylamide(PAM) system and the compatibilizing effect of PEO-PAMblock copolymcr formed during highspeed stirring of PEO/PAMmixture in its aqueous solution were studied. As viewed from thermodynamics, PEO/PAMis incompatible; the same is true of the conclusions drawn from contrast microscopy, TEM, SAXSand stress-strain behavior testing. It is found, however, that PEO-PAMblock copolymer is an effective compati-bilizer, which could cut down the dimension of the domains, reduce the heterogeneity of the system, increase the thickness of transition layer and improve the mechanical properties of the polyblend.