The study is focused on the minimization of dredged mud produced by construction and maintenance of port and waterway engineering.By adding polyacrylamide (APAM) and polyaluminum chloride (PAC) to dredged mud，the composite flocculation test of rapid separation of solid particles from dredged mud was studied.The effects of composite flocculation on the sedimentation time of mud，sediment moisture content and sediment permeability were investigated.The results show as follows：1) Compound flocculation effect of APAM and PAC is better than that of single APAM or PAC.Among the test，the APAM plays a key role in the mud sedimentation time while the PAC plays a key role in the clarity of the upper liquid of mud.2) Compound flocculation of APAM and PAC can reduce sediment moisture content effectively.While with the increase of the addition of APAM or PAC，the sediment moisture content maintains an upward trend.Namely，small amount of APAM and PAC is more beneficial to the reduction of sediment moisture content.3) Compound flocculation of APAM and PAC can enhance sediment permeability，and there exists an optimal addition amount of APAM.4) APAM is superior to PAC in reducing mud sedimentation time，decreasing sediment moisture content and increasing sediment permeability.For 2.4 ratio of silt to clay content of dredged mud，the suitable addition amounts of compound flocculation is 1 600 gt PAC and 240 gt APAM.The research results can provide reference for engineering.