Objective: To study the free radical scavenging capacity and antioxidant activity of total flavonoids of Saussurea involucrate in vitro. Method: Eight methods

namely the in vitro scavenging of 2

2-diphenyl-1-picrylhydrazyl radical (DPPH·)

2

2-nitrogen based bis-(3-ethyl benzene and thiazole-6-sulfonic acid) diamine salt cation radical (ABTS+·)

superoxide free radicals (O2-·)

hydroxyl radical (·OH)

nitric oxide (NO) and the determination of metal chelating capacity

reducing power and total antioxidant capacity

were adopted to evaluate the capacity of free radical scavenging capacity and antioxidant activity of total flavonoids of S. involucrate. Result: Total flavonoids of S. involucrate can effectively scavenge DPPH·

ABTS+·

·OH

NO at certain concentrations. Its 50% inhibition concentration(IC50) values for DPPH·

ABTS+·

·OH

NO were 52.52

71.71

60.38

203.95 mg·L-1

respectively

and its IC50 for O2-·was 271.06 mg·L-1

which was less than vitamin C(VC

380.10 mg·L-1)

and its concentration of half metal chelate was 184.52 mg·L-1. Moreover

it also had a certain reducing power and total antioxidant capacity. Conclusion: Total flavonoids of S. involucrate has a strong free radical scavenging capacity and antioxidant activity in vitro and are type of natural antioxidant substances with a high research value and potential.