Abstract: The two-year-old seedlings of Lagerstroemia indica L. ‘Ebony Embers’,an excellent new variety of Lagerstroemia indica L.,were employed for the research object, five flooding length treatments was set up and the flooding in pots method was used to ascertain the effects of various flooding stress treatments on the growth and physiological indexes of Lagerstroemia indica L.seedlings, in order to provide reference for water management in the culture of Lagerstroemia indica L. seedlings and garden application.The results showed that Lagerstroemia indica L. could tolerate up to 14 days of flooding, with 21 days representing the maximum amount of flooding stress that the species could withstand.As the duration of flooding stress increased, the relative water content, peroxidase activity, superoxide dismutase activity, soluble protein content, net photosynthesis rate（Pn）,stomatal conductance（Gs）,transpiration rate（Tr）,and inter-cellular CO₂ concentration（Ci） of Lagerstroemia indica L. seedlings showed a decreasing trend.At 21 days of flooding, these values were significantly lower than those of the control falling by 24.29%,79.88%,18.66%,3.16%,80.45%,92.51%,93.10%,and 25.43%,respectively.They reached their lowest value at 28 days of flooding.Proline content and malondialdehyde content showed an upward trend, and increased significantly by 67.34% and 360.54%,respectively, compared with the control at 21 days of inundation, and reached the maximum at 28 days of inundation.Catalase activity showed a trend of increasing and then decreasing, and reached the maximum at 21 days, and increased significantly 252.65% over the control compared with the control.Soluble sugar content showed a trend of decreasing and then increasing and then decreasing, with the flooding 21 days being the largest, a significant increase of 19.38% over the control.The relative chlorophyll content of Lagerstroemia indica L. seedlings during the period of flooding stress did not change significantly.Water use efficiency（WUE） showed an undulating and fluctuating trend, with the control being the lowest and the flooding 21 days being higher, which was a significant higher than the control by 184.00%.Although Lagerstroemia indica L. seedlings may withstand some flooding, the duration of the flooding stress should not be longer than 14 days.