Abstract: A spectrophotometric method was established for determining 2,2-diphenyl-1-picrylhydrazyl (DPPH)free radical scavenging activity of natural antioxidants. The evaluating criterion of DPPH free radical scavenging activity was regarded as"IC50" by determining the scavenging rate curves of rutin, quercetin,ascorbic acid and gallic acid. The DPPH free radical scavenging activity of extract from Toona sinensis (A.Juss.)Roem. leaves was expressed by IC50. The condition of scavenging DPPH free radical of extracts from T. sinensis. leaves was determined by change of absorbency veriety at wavelength 517 nm after reacting DPPH with extracts. It was wavelength 517,reacting time 50 min. Under this condition, IC50 of scavenging DPPH free radical of extracts from T. sinensis leaves is 22.026.