Diabetes is an urgent health issue characterized by ethnic and regional variations, and is inseparable from the different dietary habits. It is worthy to note that the incidence of diabetes in Bai nationality has been reported to be much lower than Han in China. As a daily vegetable of Bai, the phytochemical and antidiabetic study of Ottelia acuminata var. acuminata had not been carried out. In this study, 41 metabolites with diverse diarylheptanoid (six new ones, Otteacumienes A-F), flavone, sesquiterpenoid, coumarin, lignan, polyacetylene, and alkaloid skeletons were characterized from O. acuminata var. acuminata. Among them, the racemic nature of 3 was characterized by chiral resolution and calculated ECD methods. The biological study revealed diarylheptanoids showed significant alpha-glucosidase inhibitory activities with 5 as the most effective one (60-fold stronger than acarbose). Molecular docking studies indicated that these structures have different binding cavities with acarbose. This study demonstrated that O. acuminata var. acuminata might correlated with the low incidence diabetes of Bai and the diarylheptanoids may have potential therapeutic value for diabetes mellitus.