Abstract: Chitosan/gelatin hydrogels were prepared through the reaction between natural chitosan and gelatin. Swelling ratios of the hydrogels in buffer solutions at different pH values were studied. The structure was confirmed by FTIR and SEM. The results showed that the hydrogels were strongly pH-sensitive and the swelling ratio of the hydrogels in acid medium was higher than that in alkaline medium. Furthermore，the largest swelling ratio was obtained in a pH 3.0 buffer solution and the smallest was obtained in a pH 9.0 buffer solution. The hydrogels had good swelling-contracting reversibility in the solution which pH value was alternately changed. With the increase of glutaraldehyde dosage，the SR of the hydrogels decreased in buffer solutions at different pH values.