Grafting of linear low density polyethylene ( LLDPE) is an important method used in the modification of functional group. The method of c- ray irradiation grafting of trifluoroacetic acid allyl ester onto LLDPE was studied. The c- ray irradiation causes molecular bond scission and produces free radical sites on the LLDPE. This process was carried out at 500 kGy c- ray irradiation doses from a 60 Co source and the optimum concentration ( 30 wt%) of trifluoroacetic acid allyl ester. The microstructure of modified polymer film has been characterized by fourier transform infrared ( FT- IR) and nuclear magnetic resonance ( NMR). Thermal properties of the grafted products were also studied by thermogravimetric analysis ( TGA).