Abstract: Effects of single and combined stress of Cu and Zn on chlorophyll content and scavenging system of activated oxygen in leaves of Ludwigia prostrate Roxb were studied by cultivation experiments. The results showed that the activity of SOD and contents of chlorophyll increased firstly in lower concentration of Cu (100 mg/kg) and Zn (100 mg/kg). At the same time, electric conductivity and MDA content of leaf cells decreased. Those may be regarded as a protecting function of plants. With the increase of concentration of Cu and Zn, the activity of SOD decreased. When the concentration of Cu & Zn was 800 mg/kg, the activity of SOD were 67.05% and 53.58% of the control, respectively. While the activity of POD increased gradually and took important parts in antioxidation at higher concentration of Cu and Zn stress. The content of MDA of Cu (200 mg/kg) + Zn (800 mg/kg) & Zn (200 mg/kg) + Cu (800 mg/kg) was enhanced with Cu, Zn concentration increasing. Compared with the control they were increased by 110% and 130%, respectively. The activity of CAT had little effect. The results indicated that Cu and Zn stress affected scavenging system of activated oxygen and resulted in imbalance of activated oxygen metabolism.