Asprosin was a novel secreted adipokine which was induced by fasting and promoted hepatic glucose release. Circulating asprosin displayed circadian oscillation with an acute drop coinciding with the onset of feeding in healthy humans. The present study investigated whether this circadian oscillation still existed in type 2 diabetes mellitus (T2DM).We recruited 60 patients with T2DM and 60 normal glucose tolerance (NGT) subjects. All participants completed a 75g oral glucose tolerance test (OGTT). Fasting and 2h postprandial serum asprosin concentrations were measured via ELISA method. Partial correlation coefficients were calculated to analyze the relationships between serum asprosin level and parameters of glucose metabolism. Multiple logistic regression analysis was used to determine the association of serum asprosin level with diabetes.Both fasting and postprandial asprosin levels were significantly higher in patients with T2DM. Postprandial asprosin level was apparently lower than fasting asprosin level in NGT subjects. Fasting asprosin level closely correlated with T2DM after multiple adjustment (OR=2.329, P = 0.023). △Asprosin correlated negatively with △BG (r = -0.502, P ＜ 0.001) and △C-peptide (r = -0.467, P ＜ 0.001) in NGT subjects, but not in T2DM patients.Serum asprosin level decreased coinciding with the onset of OGTT in NGT, wihle this circadian oscillation was disturbed in T2DM. The impaired response of asprosin to glucose fluctuation in T2DM might be one of reasons for the onset of T2DM.