Abstract: More and more ultra soft soil improvement projects need to be executed at present in China. Based on some improvements of the traditional vacuum preloading method, a new technology for improving the surface-layer of the ultra soft soil by vacuum preloading is developed. The recyclable three-dimensional drainage cushion made of polythene is used to replace the sand cushion, which solves the laying problem of the sand cushion on the ultra soft soil and can be a solution of the continuous increasing of the cost in vacuum preloading projects owing to the increasing price of the natural sand. The plate of foam plastic is used to construct the float bridge, which provides a steady platform for the transportation of construction materials. The water-stop dike is built along the float bridge, which can also divide the wide area of ultra soft soil ground into several portions for improvement. Woven fabrics and non-woven fabrics are laid on the surface of the ultra soft soil, which can provide the platform for the installation of the prefabricated vertical drain. A typical application project is given to illustrate this technology.