It is well known that small amount of mineral acid gave a obvious enhancement to radiation grafting yields for some typical systems such as the grafting copolymerization of styrene in methanol onto polyethylene, polypropylene and other polyolefins. But in the case of segmented polyetherurethane as the matrix, the radiation grafting yield of N-vinyl-2-pyrrolidone on it would be optimum only in basic media.,In this investigation the radiation grafting copolymerizations with some monomers such as acrylamide, acrylic acid, 4-vinyl-pyridine and styrene were performed. The radiation grafting efficiencies of these systems were shown to be enhanced as well in the grafting systems with higher pH values. Primary explanation was given.