Abstract： ObjectiveTo observe the effect of chronic hype rg lycemia on islet β cells in type 2 diabetes mellitus with secondary sulfonylure as failure.MethodsThere were 51 cases with type 2 diabetes a ttending in the study. Standard bread test and arginine stimulating test were co mpleted in all patients before and after plasma glucose were controlled. Gliben clamide test was completed after plasma glucose were controlled. Acute insulin r esponse to arginine(AIR ARG ), insulin response to glucose (IRG) and the m odified beta-cell function index(MBCI) were observed during the study.ResultsThere were not significant difference in AIR ARG , IRG, and MBCI before and after glucose were controlled in all 51 cases. AIR ARG were higher in patients with islet β cells response to glibenclamide than in p atients without response to glibenclamide before plasma glucose was controlled (P<0.05). AIR ARG , IRG, and MBCI were higher in patients with β cells response to glibennlamide than in patients without response to glibenclamide aft er plasma glucose was controlled (P<0.05). IRG and MBCI were improved in pat ients without response to glibenclamide after glucose was controlled (P<0.05 ). All of AIR ARG , IRG,and MBCI were not significantly varied in patients with responseless to glibenclamide during study.ConclusionsC hronic hyperglycemia impaired islet β cells function. The function of β cells was partially improved in part of type 2 diabetic patients with secondary failu re.