Abstract: Simulator was adopted to set different water flow disturbance strengths (0, 5, 15, 30, 60 L/h), analyzes the migration and transformation of P forms and the changes of P concentration in the sediments under different water disturbance intensity. The results showed that the water flow disturbance intensity of 0-15 L/h promotes the release of P from the sediment, and 30-60 L/h inhibits the release of P, 15 L/h of water disturbance intensity caused the maximum release amount and release rate of TP in water. Under the influence of water disturbance, the TP, weakly adsorbed phosphorus (Labile-P), reducible phosphorus (RSP) and calcium-bound phosphorus (Ca-P) of the sediment were released to some extent, and the TP release increased first then decrease with the disturbance intensity, and the release patterns of the 3 P forms were different, and the TP in the water was significantly positively correlated with the RSP and Ca-P on the 30^th day (P<0.01). The P form in the sediment is affected by the water flow disturbance, and the conversion trend from active P to inactive P is obvious. The P activity ratio decreases firstly then increases in the 15 L/h water flow disturbance intensity. It showed that the water flow disturbance intensity could control the P pollution of the ditch and reduce the ecological risk of the ditch sediment to a certain extent.