By studying on absorption spectrum of DPPH solution and DPPH reaction system, the conclusion was drawn as follows, the wavelength for the determination of DPPH reaction system by spectrophotometric method was chosen to be 518.4 nm, DPPH reaction system was 4.00 mL of 257.7 mg x L(-1) DPPH+1 mL of antioxidant solution with the reaction time of DPPH reaction system of 40 min. The relation between DPPH radical scavenging rate and the concentration of TBHQ and BHT was studied, and IC50 (the value of antioxidant concentration for scavenging half of DPPH radical) was used as the index to evaluate scavenging capacity. The determining IC50 values were as follows: TBHQ (21.14 mg x L(-1)), BHT(42.09 mg x L(-1)) and M40 (108.40 mg x L(-1)). Bamboo leaf extract could be used as natural antioxidant.