Abstract: Objective:The effect of molecular weight of chitosan on the release properties of SO₂ from SO₂ sustained-release materials of chitosan was investigated. Methods:Chitosan-type SO₂ sustained-release material was prepared by metal ion coordination reaction,vulcanization reaction and embedding technology with chitosan as the main raw material. The sustained-release material of chitosan-type SO₂ was characterized by field emission environmental scanning electron microscopy(FESEM)and fourier infrared spectroscopy(FTIR),and SO₂ release amount was determined by iodometry. Results:The release amount of sustained-release materials prepared by a single molecular weight was greatly affected by temperature and humidity,and the release amount was unstable. The sustained-release materials made by mixing the products of sulfur-containing chitosan skeleton molecules with the molecular weight of 50 kDa and sulfite chitosan embedding products with the molecular weight of 150 kDa were the least affected by temperature and humidity. In the first 4 d,the release amount of SO₂ was significantly increased(P<0.05),and the released amount above 50 mg·g^-1 at 4~30 d. After 30 d,the released amount gradually decreased. Conclusion:The sustained-release material of chitosan-type SO₂,which was composed of the products of sulfur-containing chitosan skeleton molecules with the molecular weight of 50 kDa and the sulfite chitosan embedding products with the molecular weight of 150 kDa,was superior. The product was powdery and dark green. The main elements and atomic contents were 21.23% C,36.00% O,10.70% S and 32.08% Cu. There were -OH,-NH,C-H and amide bonds in the products analyzed by infrared spectroscopy.