we investigated the effect of ZnO nanoparticles on the antioxidant enzyme activities of the Thai rice plants (Chainat1 cultivar). we compared the antioxidant enzyme activities of the treated plants and non-treated plants respond to ZnO nanoparticles treatments. Rice plants grown for 37, 44 and 51 days with various concentrations (100-800 mg.L) of ZnO nanoparticles were observed the dynamic changes of catalase and peroxidase enzyme activities.