Hovenia acerba Lindl is a traditional food or medicine homologous to food and medicine， which has the effects of lowering blood sugar and pressure， relieving alcohol and protecting liver. However， the mixed use of Hovenia acerba Lind pulp and seed brings a lot of inconvenience to its application and inspection. In order to determine the active site of Hovenia acerba Lind， the effects of water and 95% ethanol extract from pulp and seed on α-glucosidase activity in vitro and Streptozocin(STZ) -induced hypoglycemic activity and its substance basis in type II diabetes model mice were studied. The results showed that seed ethanol extract(SEE) was the main active substance for inhibiting α -glucoside， and the IC50 of SEE was 0.97 mg/mL， which was a competitive inhibitor. The water extract of pulp (PWE) was the main active substance， and the IC50 of PWE was 2.28 mg/mL， which was a mixed inhibitor. The inhibition activity of α-glucosidase in SEE and seed water extract(SWE) was higher than PWE and pulp ethanol extract (PEE). Animal experiments showed that the four extracts could reduce the blood glucose and improve the glucose tolerance and body weight of the mice to varying degrees， but the SEE had the most significant effect (P < 0.01). Overall， the order of hypoglycemic activity was SEE>SWE>PWE>PEE， seed is the main active part of Hovenia acerba Lind in lowering blood glucose， and its hypoglycemic effect is stronger than that of pulp. Five compounds were isolated and purified from the SEE by silica gel， C18 medium pressure liquid chromatography and Sephadex LH-20 column chromatography. Compounds 1-5 were identified as quercetin， dihydroquercetin， myricetin， dihydromyricetin， and quercetin-3-O-β-D-glucopyranoside by ESI-MS， 1HNMR， 13CNMR， HSQC and HMBC. This study provided a theoretical basis for solving the problem of Hovenia acerba Lind pulp and seed mixing， and provided a new way for further development and utilization the resources.