Abstract:The leaves of Carica papaya seedlings cultured in pots were sprayed on both surfaces with free radical scavengers, i.e. vitamins C (10 mmol/L), E (6 mmol/L) and sodium benzoate (5 mmol/L), respectively one day before water stress treatment. Soil in pots was dried naturally to 12%-14% of moisture content, whereas for control at 60%-65%. The results showed that the pretreatment with free radical scavengers could effectively decrease the increment level of plasma membrane permeability, POD activity, MDA and H2O2 contents, retard the decrease of chlorophyll and soluble protein contents and the SOD activity in papaya under water stress. Among the free radical scavengers, the protective effect of vitamin C was best.