Objective: The α-glucosidase inhibition （α-GI） activity of dark blue pigment from the leaves of Vaccinium bracteatum Thunb. （VBTL） was investigated to confirm the benefits of regulation of postprandial blood sugar. Methods: The dark blue pigment prepared by purified iridoid compounds and exogenous amino compound was used to study the inhibition effect and the inhibition kinetic by Lineweaver-Burk reciprocal curve method. Fluorescence emission spectrum was used to analyze the interaction between the pigment and α-glucosidase. Results: The VBTL dark blue pigment had higher inhibitory effect on α-glucosidase. The α-GI activity increased with the increasing concentration of dark blue pigment and the IC₅₀ value was 0.373 mg/mL. The inhibition kinetic analysis showed that the α-glucosidase inhibitory effect of dark blue pigment was competitive and non-competitive mixed inhibition types. Fluorescence spectrum analysis showed that the static quenching model was happened between α-glucosidase and pigment molecules, and this interaction caused the unfolding of the α-glucosidase molecule structure. Conclusion: The α-GI activity of dark blue pigment from VBTL was verified its beneficial effect on regulating postprandial blood glucose, and provided the scientific basis for the development and utilization of pigment of VBTL.