Abstract: The effect of phosphorus-free α-FeOOH on the adsorption/desorption kinetics of phosphorus(P) and solid concentration effect of the resuspended sediments collected from Chengdao Oilfield in Bohai Sea were studied using batch experiments.The results indicated that α-FeOOH improved the rate, capacity of sediments adsorbing P, and the ratio of the amount of P adsorbed at fast stage to that at kinetic equilibrium on the sediments.In addition, the ratio of the amount of P desorbed to that pre-adsorbed on the sediments decreased with increasing α-FeOOH content, suggesting that α-FeOOH was unfavorable for sediments desorbing P.Freundlich coefficient (K_F) ratio of sediments of 10 g/L to 2 g/L was closer to 1 with increasing α-FeOOH content in sediments, which meant the weakening of solid concentration effect.The effect of a concentration change of sediments on reversibility can be explored through the equation K_F=a*S^-b.The index of solid concentration effect, b, decreased with increasing the α-FeOOH content in sediments, which revealed that the potential mechanism of α-FeOOH weakening solid concentration effect was through reducing reversibility.This research provides an example for weakening the solid concentration effect under conditions of increasing the irreversibility of an adsorption system.