Abstract: Taking Crepidiastrum denticulatum as test merterial, the total flavonoids in the roots, old stems, tender stems, leaves, flower buds, flowers and seeds of Crepidiastrum denticulatum were extracted by ultrasonic extraction with 60% ethanol, the contents of total flavonoids and antioxidant activities such as DPPH,hydroxyl radical scavenging activity and reducing power were determined by spectrophotometer.The contents of total flavonoids in different parts of the plant were determined and their antioxidant activities were compared, in order to provide reference for the development and utilization of the medicinal resources of Crepidiastrum denticulatum.The results showed that the total flavonoid contents of seed extract(3.75 mg·g^-1) were higher than those of leaves(2.14 mg·g^-1),buds(0.93 mg·g^-1),blooming flowers(0.69 mg·g^-1),tender stems(0.44 mg·g^-1),roots(0.34 mg·g^-1) and old stems(0.17 mg·g^-1).The scavenging capacity of DPPH free radical, hydroxyl free radical and Fe²⁺ reduction capacity of the extracts from different tissues were also different, and there was a dose-effect relationship between the antioxidant activity and the content of total flavonoids in the extracts.The antioxidant activity of total flavonoids in seeds was the strongest.For the purpose of extracting flavonoids, Crepidiastrum denticulatum was suitable for harvesting in the mature stage of seeds.Because the yield of leaves was higher than that of seeds, the content of flavonoids was the second to the seed, so it is also possible to select the period of vigorous leaf growth to harvest.