Vacuum preloading is a ground improvement technology for the drainage consolidation of soft soil.This technology combines vacuum pumping and prefabricated vertical drains (PVD) to increase the effective stress of the soft soil at different depth to reinforce the soft soil.However,some scholars believe that the vacuum pressure gradually decreases with depth,thus vacuum preloading has a better reinforcing effect on the shallow layers than on the deep layers,bringing controversy on the design and construction of vacuum preloading.In order to settle this controversy,a comparative analysis is conducted on shallow and deep soil layers from three perspectives:vacuum load distribution,ground settlement,and undrained shear strength.Combining theoretical research and field data,it is proven that the additional load of vacuum preloading at different depths is equal,and its reinforcement effect on soil layers at different depths is the same.In actual engineering,the reinforcement quality evaluation indicators such as ground settlement and the increase ratio of undrained shear strength are larger in shallow layer than in deep layer,but this does not mean that the reinforcement of vacuum preloading is better for shallow layer than for deep layer.The difference in the above reinforcement quality evaluation indicators is due to the initial effective stress state of the soil itself,that is,the initial vertical effective stress of shallow soil is lower than that of deep soil.