Abstract: Effects of CrCI₃ stress with different concentrations on some earlier physiological and ecological characteristics of seed germination of Casuarina equisetifolia were studied．The results show that the seed germination percentage，the plant height，root length，fresh biomass，and dry biomass of seedlings all gradually decrease with the treatments of increased CrCI₃ concentrations．At the meantime，the contents of proline and superoxide anion(0₂^-)increase firstly and decrease afterwards，and the content of protein gradually increases．Furthermore，the activity of the protective enzyme SOD increases firstly and decreases afterwards，and the activities of POD and CAT both gradually increase．The activities of SOD ，POD，CAT can act as sensitive designators to poison，and the morphologic responses of plant usually lag behind the physiological responses when it is under the environment stress．