Abstract: The subsoil formed a double-layer structure during the dynamic compaction. Summarized from extensive in-situ test results, both the upper layer(A) and lower layer (B) have their own distinctions and independent each other. The interface of A and B occurs in the location of critical level of dynamic stress during the compaction, layer A is the area of densely compacted, most of the particles have a large deformation imparted by the high destructive stress, whereas layer B pertains to poorly compacted area with the character of small deformation and doesn’t lead to collapse with regardless of the number of blows. If the proper design and a treatment procedure are induced in the compaction, the upper can achieve a good bearing layer, which has a exponent increasing in bearing capacity value compared with that of to be treated, the bearing capacity of lower layer approximately to keep the average level of before treated soil even though with little fluctuated. From the practical point of view, the principle work is to entirely investigate the character and the thickness of upper layer, and to get a general knowledge to the definite depth of lower layer.