Grafting polymerization of acrylonitrile onto low density polyethylene film was studied further following the earlier work [1]. A novel and effective method was developed to directly determine the number of end-groups, i.e. phenyls at the end of grafted chains with UV-vis spectroscopy; according to the number of phenyl end-groups and the weight of grafted polymers, grafting chain length and density were estimated; investigations indicated both of these two parameters could be practically controlled. Grafting polymerization of acrylonitrile onto low density polyethylene film was studied further following the earlier work [1]. A novel and effective method was developed to directly determine the number of end-groups, i.e. phenyls at the end of grafted chains with UV-vis spectroscopy; according to the number of phenyl end-groups and the weight of grafted polymers, grafting chain length and density were estimated; investigations indicated both of these two parameters could be practically controlled.