A method for preparing a Hovenia dulcis Thunb extract rich in dihydromyricetin includes the following steps: (1) crushing Hovenia dulcis Thunb seeds to obtain a Hovenia dulcis Thunb powder; (2) adding a 10-95% ethanol solution in an amount of 3-15 times of an amount of the Hovenia dulcis Thunb powder, stirring and extracting at 20° C.-80° C. twice; (3) filtering to obtain an extract solution; (4) concentrating the extract solution by evaporating ethanol under reduced pressure to obtain a crude extract, the crude extract having a solid content of 10%-40%; (5) placing the crude extract at −20° C. to 8° C. for 0.5 to 12 hours; (6) centrifuging the crude extract to obtain a supernatant; and (7) spray-drying the supernatant to obtain the Hovenia dulcis Thunb extract.