The study focused on the modification of chitosan by cyanoethylation. The product was dissolved in water at proper concentration and sprayed to the surfaces of paper. Tensile strength, folding endurance, glossiness, dry-heat ageing resistance and FT-IR tests were conducted on those samples. The results showed that the paper treated by 30% cyanoethylated-chitosan glue contained its origin feeling, glossiness and color, meanwhile compared to the untreated paper tensile strength was increased by 67% and folding endurance was increased 5.5 times. It proves that cyanoethylated-chitosan has good effect on the protection of paper historic relic.