pH-sensitive hydrogels based on carboxymethylchitosan (CMCTS) were synthesized by using glutaraldehyde as cross-link agenl The effects of the degree of deacetylation of CMCTS and the dosage of erosslinker on the swelling behaviors of hydrogels have been studied The results show that the two factors related above regulate their swelling behavior At pH=3.0

the hydmgel shfinked most while swelled at pH：1 0

5．0

7．4

9 0．In general

the swelling ratio (SR) of this hydrogel in alkaline solution is much larger than that in acidic solution．The release behavior of salicylic acid(SA)entrapped in the hydrogels was of distinctly difference with the changes of pH value of loading medium and the semidiameter of the hydrogels．The release of salicylic acid in CMCT hydmgel in the medium of pH=1.0 was much quickerin pH=7.4

12.0

andtherelease speed and release ratioincrease with the partical size．