The effect of some factors on the graft copolymerization of styrene tO polyvinyl alcohol induced by γ-irradiation has been studied，and a preliminary estimation was made on the properties of the graft products．The grafting occured very readily if a proper amount of water was added to the system． It was shown that the rate of grafting in-creased sharply with the increase of water content in the polymer film and then levelled off．while the rate of homopolymerization increased more slowJY and levelled off rapidly at a lower water content．The effect of dose rate on the grafting process at room tem-perature was studied，and it was found that the grafting was entirely diffusion—controlled with the dose rate larger than 100 r／min．at which the dose rate exponent of the relation V=KP approached zero．The plot of the amount of grafting with temperature in the range of 10—80℃ passed through a maximum at 60℃ and then fell off，while the homo-polymerization increased steadily all over the temperature range and showed an auto-acceleration at temperatures above 60℃ presumably owing tO the gel effect．The presence of oxygen has an inhibiting effect on the grafting．It was found that the homopolymeriza-tion could be remarkably inhibited，with only slight reduction in the grafting，by the pre-sence of a proper amount of oxygen or air．The graft product is soluble in dimethylformamide at 150℃．The swelling ratio of the product in boiling water or in boiling benzene was found to change linearly with the grafting．It was also found that the resistance of the film to acid or alkali was signifi．candy improved by the grafting．