Levels of hydrogen peroxide in plant extracts were overestimated by the method of only using titanium(Ⅳ) because of the interference of pigments and other materials while underestimated by the method of adding activated charcoal(A.C.) in 5% trichloroacetic acid extracts to remove pigments. These problems were avoided by a developed method of extraction, which could not only remove the pigments in acetone extracts conveniently but also get a high recovery more than 95%. Hydrogen peroxide was determined by its reaction with the complex of titanium(Ⅳ)and 4-(2-pyridylazo) resorcinol against references catalase-treated. The minimum concentration of hydrogen peroxide determinated in this essay was 0.25 μmol·L^－1. Levels of hydrogen peroxide in leaves of some plant species ranged from 0.1～0.8 μmol·g^－1.