In view of the flaws of long-delayed settling time of the dredger filling mud and slow consolidation speed of the dredged soil foundation, a research has been carried out, with the slurry in Pingyang area, Wenzhou as the object of study. With the addition of polyaluminum chloride (PAC), sodium silicate (Na2SiO3), sodium silicate (Na2SiO3) and diatomite composite reagent to the dredger mud with initial water content of 500%, an observation can be made of the height characteristics of mud water interface by adopting mixing static precipitation method. The test results show that the addition of applied reagents in the mud exerts an obvious effect on the sedimentation rate of the mud, with the positive effect of adding mixed reagent more obvious than that by adding single reagent. The results of contrast tests show that the positive effect of the combined coagulant with the mass concentration of 5 g/L and diatomite 15 g/L proves to be the most obvious with the fastest sedimentation rate and the best final settlement performance of the hydraulic-dredged mud.