Abstract: The flavonoids from Ampelopsis grossedentata were extracted respectively by the best extraction technology of ultrasonic auxiliary hot water method, ultrasonic auxiliary ethanol method, ethanol leaching method and enzyme method.The content of flavonoids were determined by spectrophotometry using chromogenic reaction of AlCl3.Choosing the ultrasonic auxiliary ethanol method from which the content of flavonoids was the highest to determine the content of different periods and different parts.The anti-lipoperoxidation activity in vitro on the liver homogenate of mouse which was made by the flavonoids in Ampelopsis grossedentata leaves and vitamin C was studied contrastively.The result showed:the content of flavonoids in different periods and different parts had evident difference.Namely, the content in leaves was much higher than in stem (41.25%) ;the anti-lipoperoxidation effect of the flavonoids in Ampelopsis grossedentata leaves was evident stronger than vitamin C and it showed did relationship within the experimental concentration range.