The concepts of lake ecological water levels at yearly，monthly and daily scales were proposed to support scientific water resources regulation of the Poyang Lake.The lake ecological water levels at different time scales include minimum，suitable and maximum ecological water levels.The frequency curve method was applied to analyze the ecological water levels at yearly，monthly and daily scales of the Poyang Lake.At yearly scale，the minimum，suitable and maximum ecological water levels of the Poyang Lake are 12.07 m，13.40 m and 15.15 m，respectively.The lake ecological water levels at yearly，monthly and daily scales reflect the various requirements of lacustrine ecosystem for water levels at different time scales.Water level data at yearly，monthly and daily scales is suggested to be applied to analyze the ecological water level at corresponding time scales.