To solve the problem of suspension diffusion in dredging engineering，a cutter suction experiment device is designed.The best operation parameters are determined by the orthogonal experiment.PSF and CPAM were added in the process of strangulation，and the anti-diffusivity of the overlying water was studied by changing the turbidity and the diffusive height of the sediment.The result shows that the reamer rotating speed is the key factor to the cutter-suction experiment.In the process of cutter suction，PSF and CPAM can reduce the turbidity of overlying water，control effectively the diffusion height of sediment and improve the water quality of overlying water.The performance of PSF was better than CPAM in controlling turbidity，which could be suppressed below 40 NTU in the case of adding PSF as optimum dosage.Adding PSF and CPAM can effectively inhibit the diffusion of suspended solids and avoid the secondary pollution to the surrounding environment.