Abstract: In this study, different amounts of aqueous extracts [0, 5, 15 and 30% (v/v)] and decompose of Eucalyptus leaves [(0, 3 and 6% (w/w)] were applied to Phalaris in pot culture and evaluated on growth parameters and antioxidant enzymes activity. The results showed that most of the growth parameters of phalaris were decreased when exposed to different amounts of decompose and water extracts of Eucalyptus leaves, especially in the leaf decompose. Also, antioxidant enzymes activity in root and shoot of Phalaris were affected by aqueous extracts and decompose of Eucalyptus leaves. The findings indicated that decompose of Eucalyptus leaves decreased catalase activity and increased ascorbate activity in root and shoot of Phalaris in comparison to control while aqueous extract of Eucalyptus leaves significant raised ascorbate peroxidase in Phalaris root. Activity of other enzymes such as polyphenol oxidase and peroxidase in Phalaris affected less aqueous extracts and decompose of Eucalyptus leaves.