Abstract: Effects of single and combined pollution of La and Zn on reactive oxygen scavenging system in leaves of Lemna minor were studied.The results showed that both La and Zn,applied at a rate of 20 mg·L^-1,caused obvious damage to Lemna minor,but the latter was much higher than the former in toxicity to the plant.Combined application of La and Zn weakened their respective toxicity to a varying extent,which was demonstrated in slower decline of chlorophyll and soluble protein content and CAT activity,higher GSH and AsA contents and SOD activity,as well as the decline of POD activity.So in terms of toxicity to Lemna minor,the three treatments were in a decreasing order of Zn,La,La+Zn.La and Zn may have interactive relieving effect,which is supposedly related to enhancement of the ability of the reactive oxygen scavenging system in the plant.