After consolidated by vacuum preloading, recently superficial hydraulic filled mud soil commonly forms a small region, which has a higher strength around the drainage plate. This zone with a higher density, greater shear strength and small settlement, is so-called the “soil pile”. The poor consolidation result of the region outside the “soil pile” causes uneven reinforcement phenomenon in a large blow filled silt field. To analysis this phenomenon, we firstly conduct an indoor model test of superficial hydraulic filled mud soil under vacuum preloading to research the particle composition, settlement, pore pressure head height and water content. Secondly, we adopt numerical analysis software PFC2D to explore particle’s forming mechanism from the micro sight. The indoor model test shows that uneven settlement is formed in soil after vacuum preloading. Obvious uplift is developed around the drainage plate with the radius of 20 cm to 25 cm. The content and density of fine particle gains highly, and its permeability coefficient decreases around the drainage plate, forming a relatively dense and weak permeability “pile” phenomenon. The numerical simulation indicates that under the influence of negative pressure, particles moving down results soil’s consolidation. With the effect of negative pressure in drainage plate, soil particles nearby drainage plate move to drain board direction which result in the “soil pile”.