Abstract: Antioxidative substances of Acer truncatum leave were extracted with 70% ethanol.Their antioxidative activities were essayed by microbiological paper method and DPPH method.The effects of light,heat,pH and sodium chloride on the stabilities of these antioxidative substances were also studied.It was found that the total flavonoid of the extracts of Acer truncatume leave showed strong scavenging effects on DPPH radical and the 1O2 produced from microbiological paper system.The extracts were resistant to heat and light and the solution of could exist stably in acidic medium and sodium chloride.