Based on located monitoring,morphological characteristics,biomass,photosynthesis and resource utilization of Vetiveria zizanioides at flooded and non-flooded areas were studied on the hydro-fluctuation belts in the Three Gorges Reservoir and the adaptation mechanism was discussed.The results showed that:(1)V.zizanioides can still live within 4 months of yearly flooding at the maximum depth of 9 m.(2)Compared with the V.zizanioides at the non-flooded area,most of the aboveground morphological characteristics of V.zizanioides at the flooded area decreased and the margin varied as the time of restore growth varied.(3)The total biomass,aboveground biomass,T_r,G_s,C_i decreased by 10.58%,48.46%,20.75%,9.19% and 10.04%,respectively,and root diameter,root length,root number,root spread range,underground biomass,underground and aboveground biomass ratio,P_n,WUE and CUE increased by 12.50%,24.13%,19.09%,78.46%,30.04%,151.71%,7.23%,36.47% and 63.64%,respectively.Increasing root tillering and growth,leaf length,underground biomass and underground biomass allocation and improving water and CO₂ utilization while decreasing plant height and transpiration improving were the adaptation strategy of V.zizanioides in the Three Gorges Reservoir to flooding-drying habitat changes.