Abstract: Chitosan-acrylic acid-hydroxyethyl methacrylate（CS-AA-HEMA）hydrogel with high hardness was synthesized in acrylic acid（AA）solution with chitosan（CS）and 2-hydroxyethyl methacrylate（HEMA）using glutaraldehyde as crosslinker. Effects of concentrations of CS，AA and HEMA as well as the gel placed time on the hardness of hydrogel，and the state and distribution of water in the hydrogel were investigated. Results indicated that the hardness of CS-AA-HEMA hydrogel increased first and then decreased gradually with the increase in AA concentration，and the hardness increased obviously with the increase in concentrations of HEMA and CS as well as the extension of gel placed time. There were free water，intermediate water and non-freezing water in the CS-AA-HEMA hydrogel. When the concentration of AA was 7.257 mol/L，the hydrogel showed the highest content of equilibrium water and freezing water with 65.412% and 61.537%，respectively；while when the AA concentration was 4.354 mol/L，the hydrogel showed the highest non-freezing water with up to 13.549%. The dehydration temperature of CS-AA-HEMA hydrogel was 20—200 ℃，and the decomposition temperature was 380—470 ℃.