Aminoethyl methacrylate(AEMA) was grafted onto the polypropylene microporous membrane by photo-induced polymerization to immobilize dextran. XPS spectra confirmed the chemical change of the membrane surface after the graft polymerization of AEMA and the immobilization of dextran. The water contact angle measurement indicated that the hydrophilicity of the membrane surface can be increased reparably by the dextran immobilization.