Paper strengthening is a new application of Co60γ-radiation used for the protection of archives and books. The principle of paper strengthening is using Co60γ- radiation to carry the graft cross-linking of cellulose on papers and monomers to increase the strength of papers. The experimental papers soaked with monomers, then irradiated by suitable dosage ofγ-radiation, can induce graft copolymerization of chemical bonding between the cellulose and monomers, then produce cellulose-plastics polymers, which could increase the durability of archives and books remarkably.