The seedlings of two tree species (Schima superba and Castanopsis fissa )and two shrub species (Psychotrla rubra and A rdisia quinquegona) from a subtropical natural forest were grown in pots under 100％，36％ and 16％ natural light． The difference in activities of lipoxygenase (LOX)， xanthine oxidase (XOD) and monoamine oxidase (MAO) in leaves and the production rates of three active oxygen species (O2-., OH·, H2O2) in chloroplasts were c0mpared．Leaves grown under 100％ sun light showed highest activities of LOX and XOD．The changing trends ofO2-., OH· and H2O2 in chloroplasts responding to light intensity were significant and similar to that of LOX and XOD activities．High activities of LOX and XOD might be one of the causes of high active oxygen level in leaves that were adapted to high light intensity．The tested understory shrub plants showed lower LOX and XOD activities than the canopy tree species， but the response of enzyme activity and active oxygen production to the change of light intensity was more sensitive than tree species.