PET film surface was irradiated and grafted with hydrophilic monomer by XeCl excimer laser to improve surface hydrophilicity. The influences of laser fluence and pulse numbers on surface hydrophilicity changes of ablated and grafted PET films were studied, and the differences of surface property between ablated films and grafted films were discussed. Based on the analysis of factors influencing the weights of ablated films and grafted films, a new formula reckoning graft degree was presented.