Abstract: Based on the invented annular water tank test device,the pollutant release characteristics of river sediment under hydrodynamic conditions were studied,and the effects of in situ capping and in situ immobilization on the release control of sediment pollutants was carried out.The test results show that the river flow velocity directly affects the release characteristics of sediment pollutants.As the water flow rate continues to increase,the sediments are in three states: not started,small amount movement,and universal movement.When the flow rate is lower than the starting flow rate,the sediment is not started,and the pollutant release amount and turbidity in the overlying water are close to the hydrostatic conditions.When the flow rate is greater than the starting flow rate,the sediment is greatly started,and the amount of pollutants released from the overlying water is greatly increased.Both in situ capping and in situ immobilization can effectively control the release of sediment contaminants.Compared with untreated,the pollutant control rate after in situ capping can reach 60% ～ 90%,and the weight of the sand layer avoids the large-scale start of the sediment,which leads to a significant decrease in the pollutant content in the overlying water.The contaminant control rate after in situ solidification was 97%,but the p H of the overlying water increased after solidification,and the water was alkaline.