By studying on absorption spectrum of red compound coming from the reaction system of Fe2+ and 1,10-phenanthroline and the capacity of antioxidant TBHQ and bamboo leaf extract for scavenging hydroxyl free radical, some results were drawn as follows: the determining wavelength of bamboo leaf extract for scavenging hydroxyl free radical by spectrophotometric method is 509.1 nm, and IC50 (the value of antioxidant concentration at scavenging half of hydroxyl free radical)was used as the index to evaluate scavenging capacity. The determined IC50 values were TBHQ(0.040), M20(0.378), M40(0.323), M60(0.334), and bamboo leaf extract could be used as natural antioxidant.