The direct vacuum preloading method was applied to improve the soft clay stratum with high permeability at a harbor in North China. This method cancels horizontal drainage sand cushion and connects plastic vertical drainage (PVD) with sealed pipe network directly. The energy can be transmitted with high efficiency. The characters of the soft clay stratum were greatly improved. The advantages of such method in economical efficiency and technicality were verified. The instance could be used as a reference for similar projects.