The invention relates to the technical field of treatment of soft soil foundations, and discloses a composite structure for treating a soft soil foundation. The composite structure comprises bearing piles, pile caps, a stiffening layer and a backfilled rolled cushion layer, wherein the bearing piles are vertically arranged along the depth of the soft soil foundation; the pile caps are connected to the upper ends of the bearing piles; the stiffening layer is paved on the soft soil foundation and covers the top surfaces of the pile caps; the backfilled rolled cushion layer is paved on the stiffening layer; therefore, the whole composite structure is formed from top to bottom; the bearing piles penetrate through a soft soil layer and work on an overlaying force-holding soil layer; a basic load is transmitted through the composite structure from the soft soil layer to the overlaying force-holding soil layer; an effect of stiffening the soft soil foundation is achieved, and a few of technological processes are completed, thus shortening the construction time and improving the working efficiency; furthermore, the composite material does not need to be unloaded or removed, so that the expense for unloading or removal is saved, and the composite structure is more economical and reasonable; and moreover, the phenomenon of environmental pollution caused by earthwork unloading and external transportation is avoided, so that the composite structure goes greener and is more environmentally-friendly.