This paper aims to verify if the essential oils exacted from Chinese herbal medicines can inhibit alpha- glucosidase (a-glycosidase) activity. For this purpose, the essential oils were exacted from three Chinese herbal medicines collected from Taibai Mountain, China, namely Pyrola calliantha H. Andres (Pyrola calliantha), the flowers of Senecio scandens Buch.-Ham. ex D. Don (Senecio scandens) and the roots of Schisandra chinensis. The inhibitory activity of the three kinds of essential oils against a-glucosidase was contrasted with that of acarbose (positive control). The half maximal inhibitory concentrations (IC50) of each test substance in inhibiting a-glucosidase activity were calculated as: 0.02211 mg/mL (the essential oil of Pyrola calliantha), 0.1304 mg/mL (the essential oil of Senecio scandens flowers), 0.01925 mg/mL (the essential oil of Schisandra chinensis roots), and 23.48mg /mL (acarbose), indicating that the three essential oils boast a greater inhibitory activity against a-glucosidase than acarbose. The subsequent enzyme kinetic experiments reveal that the essential oils of Pyrola calliantha and Senecio scandens flowers have a competitive and irreversible inhibitory effect against a-glucosidase, while the essential oil of Schisandra chinensis roots has a non-competitive and reversible inhibitory effect against a-glucosidase. The research findings shed new light on the application of Chinese herbal medicines.