The researches on vacuum preloading are summarized. The mechanism of vacuum preloading is analyzed; and some problems in practice are pointed out. Loading and unloading of vacuum preloading is derived and considered as loading and unloading from minor principal stress. Unloading from minor principal stress could weaken the resilience of the soil when unloading of vacuum preloading; the soil would not appear resilient obviously
even go sinking. We have needed to design the test of modeling vacuum preloading stress path more reasonably.