The effects of 0, 1.0, 2.0 and 4.0 (x 10−3 M) α-, γ- or δ-tocopherol on chlorophyll b photosensitized oxidation of soybean oil in methylene chloride were studied by peroxide values and headspace oxygen. As concentrations of tocopherols increased, peroxide values decreased and headspace oxygen increased (P < 0.05). At 1.0 × 10−3 M, α-tocopherol showed highest antioxidant effect, γ-tocopherol second and then δ-tocopherol. α- and -γ-Tocopherols had similar effects and δ-tocopherol had lower effect at 2.0 × 10−3 M (P < 0.05). However, the three tocopherols were not different (P > 0.05) at 4.0 × 10−3 M. α-Tocopherol quenched singlet oxygen to reduce the photosensitized oxidation of oil. The quenching rate constants of α-tocopherol were 2.7 × 107M−1sec−1 by peroxide value and 2.6 × 107 M−1sec−1 by headspace oxygen.