Objective To prepare insulin-containing chitosan-thioglycollic acid conjugates microspheres and evaluate their hypoglycemic effect.Methods The insulin-containing chitosan-thioglycollic acid conjugates microspheres were prepared by the dry-in-oil method using the chitosan-thioglycollic acid conjugates which the content of thiol group was 983?mol?g-1.The hypoglycemic effect of the microsphere was evaluated by drug release test in vitro and hypoglycemic test on hyperglycemic rats.Results The insulin-containing chitosan-thioglycollic acid conjugates microspheres with an average diameter of 13?m were administered by intraduodenal and intraileal application,and gave visible decrease in plasma glucose level in 4h at a dose of 20IU?kg-1.The relative bioavailability of the latter compared to hypodermic injection was 29.9%.Couclusion The results showed that the bioavailability of oral insulin could be facilitated by insulin-containing chitosan-thioglycollic acid conjugates microspheres,and good biological availability was obtained when the microspheres were administered by intraileal application.