The phosphorus adsorption characteristics of the soil from water-level-fluctuating zone (WLFZ) have an important influence on the nutritional status of the reservoir water body. The 140m, 145m, 155m, 165m and 180m altitudes soils of Shuangjiang in Pengxi River were selected for the thermodynamic experiment of phosphorus isothermal adsorption. The mechanisms for the differences in phosphorus adsorption characteristics of soils from WLFZ have been 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, the correlation between the adsorption characteristic parameters and the physical-chemical properties of the soil samples, it is considered that the soils from WLFZ had a smaller particle size distribution, higher organic matter content and Fe content were important factors affecting the phosphorus adsorption capacity, and the different characteristics of the soils mainly were affected by winter flooding sedimentation and summer rainfall erosion. The 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.