The phosphorus adsorption characteristics of the soils in water-level-fluctuating zone (WLFZ) have an important influence on the nutritional status of the reservoir water body. In order to study phosphorus adsorption characteristics of the soils at different altitudes in WLFZ, the 140 m, 145 m, 155 m, 165 m and 180 m altitudes soils of Shuangjiang in Pengxi River were selected for the thermodynamic experiment of phosphorus isothermal adsorption. The causes for the differences in phosphorus adsorption characteristics of soils from WLFZ were discussed. The results indicated that the adsorption-desorption equilibrium concentration (EPC) and the maximum adsorption amount (Qmax) of phosphorus gradually increased with the decrease of altitude, that is, the phosphorus adsorption capacity was enhanced. Combined with the analysis of the surface characteristics of the soil particles and that of the correlation between the adsorption characteristic parameters and the physical-chemical properties of the soil samples, it was considered that the soils from WLFZ had a smaller particle size distribution, higher organic matter content and Fe content, which were important factors affecting the phosphorus adsorption capacity, and the different characteristics of the soils were mainly affected by winter flooding sedimentation and summer rainfall erosion. Soils with low altitude has strong phosphorus adsorption capacity, which has certain positive significance for controlling eutrophication of the water bodies in Three Gorges Reservoir.