[Objective ] The present paper aimed to explore the effects of low phosphorus stress on physiological indexes of Eucalyptus coleziana leaves, to provide reference basis for the study of low phosphorus resistance mechanism of E. coleziana and the popularization and planting of seedlings. [ Method]The seedlings of E. coleziana clones 1203 and 1212 were hydroponically cultured with Hoagland nutrient solution with low phosphorus concentration ( 0. 1 mmol/L) and normal phosphorus concentration ( 1. 0 mmol/ L) . After 20 days, the protective enzyme activity, malondialdehyde ( MDA) content, photosynthetic pigment content and chlorophyll fluorescence parameters of seedlings of E. coleziana clones 1203 and 1212 were measured, and single-factor analysis of variance and Pearson correlation coefficient were used to analyze the physiological indexes of leaves of E. coleziana seedlings treated with different phosphorus. [Result] Under low phosphorus treatment, the content of MDA in the leaves of clones 1203 and 1212 were 0. 0032 and 0. 0037 μmol/g FW, the SOD activity were 18. 42 and 16. 25 U/ g FW, the PPO activity were 894. 13 and 1138. 00 U/ g FW, the POD activities were 579. 67 and 471. 33 U/ g FW, the APX activities were 1598. 89 and 688. 33 U/ g FW respectively, which were significantly higher than that of normal phosphorus treatment( P < 0. 05). The total chlorophyll contents were 1. 65 and 1. 51 mg/ g, and the carotenoid contents were 0. 17 and 0. 12 mg/ g, respectively, which were lower than normal phosphorus treatment. The initial fluorescence( F 0 ) of the PS II reaction center both were both 0. 082, the non-photochemical quenching coefficients ( NPQ) were 1. 44 and 1. 35, respectively, which were higher than those of normal phosphorus treatment. The maximum fluorescence ( Fm ) were 0. 37, and 0. 40, the variable fluorescence( Fv) were 0. 29 and 0. 31, the maximum photochemical quantum efficiency( Fv/F m) were 0. 78 and 0. 79,and the actual photochemical efficiency (ΦPPSII) were 0. 31and0. 32 respectively, which were lower than that of normal phosphorus treatment. The results of correlation analysis showed that low phosphorus stress had different effects on the physiological indexes of E. coleziana seedlings, especially had the most significant influence on chlorophyll fluorescence parameters. [ Conclusion ] Low phosphorus stress can cause a large amount of MDA accumulation in the leaves of E. coleziana seedlings, resulting in irreversible damage to the leaf tissue, and then cause the abnormal function of leaf photosynthetic mechanism. However, E. coleziana seedlings can reduce the damage caused by low phosphorus stress through the comprehensive regulation of protective enzymes such as SOD, PPO, POD and APX, and NPQ, especially PPO and NPQ, which may play an important role in reducing the leaf damage of E. coleziana seedlings. [ABSTRACT FROM AUTHOR]