Paper has a high value of culture, history and scientific research as the cultural carrier of historical inheritance. However, with the passage of time and the change of environment, many paper files are aging and damaged. Therefore, it is of great significance to carry out the protection of paper archives. Chitosan, a natural material, has a good compatibility with paper fibers. In this paper, chitosan (CS) was modified by epoxy cyclohexane (CHO) and methyl methacrylate (MMA) to prepare CS-CHO-g-PMMA emulsion. CS-CHO-g-PMMA was applied to paper protection, and the effects of CS-CHO-g-PMMA on heat aging resistance, reversibility and acid-base resistance were investigated. In order to improve the mechanical strength of paper, CS-CHO-g-PMMA and phosphate ester starch (HPDSP) were blended to determine the optimum ratio. The results showed that the degradation rate of paper sample was slowed down obviously and the coating had certain reversibility. Acid-base resistance experiment showed that CS-CHO-g-PMMA could effectively resisit corrosion of external acid-base to protect the paper. The best combination ratio between CS-CHO-g-PMMA and HPDSP was: m (CS-CHO-g-PMMA): m (HPDSP) = 5:2. Under this compound ratio, the performance indexes of the paper met the requirements, conforming to the “repair as old, keep the original” and other requirements.