Considering the serious bending of the vertical drainage plate in the soft soil treatment process, a method of combining flocculant technique with horizontal mesh drainage combination with vacuum pre-pressure treatment of bagged sludge was proposed. The water content, unconfined compressive strength and shear strength of the sludge treated by the straight drainage body and the new horizontal mesh drainage body were tested, and the influence of the added amount of flocculant on the consolidation effect was compared. The test results show that the new horizontal mesh drainage can effectively improve the permeability of the soil compared to the straight drainage. The addition of 0.3% flocculant is the best ratio to improve the consolidation effect. The feasibility and effectiveness were verified of the cofferdam construction technology of the new horizontal mesh drainage combination with vacuum pre-pressure treatment of bagged sludge.