After the completion of the Three Gorges Reservoir project, a 30-m height tidal zone is formed around the reservoir. Changes in P adsorption and fixation by the soils in the zone and in fate of the phosphorus directly affect the surrounding water environment. Through batch processing and indoor incubation of samples of the yellow soil and purple soil in the tidal zone, changes in form of the iron and adsorption and transformation of P in the soils were studied. Results show that flooding significantly decreased the content of crystalline iron oxides, while increasing the content of noncrystalline iron in both soils; Under flooding the content of Olsen-P in the soils displayed a declining trend, whereas the contents of Fe-P and Al-P turned upwards; Indoor simulation demonstrates that in the two yellow and purple soils under flooding for 15 days, P adsorption capacity increased by 70.8% and 9.5%, respectively; Incubated in 0.1 mol L^-1 CaCl₂, KCl and NH₄Cl solutions at pH 5 and pH 9, separately, for 15 days, the yellow soil increased its contents of Olsen-P, Fe-P and Al-P significantly, indicating that in the soils of the tidal zone, application of K, Ca or urea might increase the content of soil available P, which could eventually lead to increase in CaCl₂ extractable P, thus affecting the phosphorus content in the water body and water quality of the reservoir.