Vacuum preloading method is adopted in soft clay treatment of the design for Vietnam Ca Mau Fertilizer Project. Some monitoring methods is adopted in course of vacuum preloading, such as vacuum degree under membrane, ground settlement, layered settlement, groundwater level, pore water pressure and deep horizontal displacement. Monitoring objectives and methods are introduced. The final settlement under preloading and consolidation degree in every stage are also been calculated. Evidences for unloading are provided.