Abstract: Based on the catalytic effect of trace amounts of iron(Ⅲ)on the oxidation of methyl orange by hydrogen peroxide in a dilute nitric acid solution,a new kinetic photometric method for the determination of traces of iron(Ⅲ) was established.The sensitivity of method is 0.015 μg·L-1 and the linear range of determination is 0-96 μg·L-1.The method has been applied to the determination of trace amounts of iron(Ⅲ) in sample of activated carbon with recoveries in the range from 99% to 105%.