NOVELTY - The composite system has a cover layer (31), a diffusion water-ventilating broken stone layer (32), an upper anti-plugging layer (35), a ventilating broken stone layer (33), a lower anti-plugging layer (36), an artificial soil layer (37) and a water collecting and discharging layer (34) from the top down. Seepage gravel (38) is placed between bottom of the diffusion water-ventilating broken stone layer and top of the ventilating broken stone layer.    USE - Composite system for treating underground wet land and high-loaded underground permeated sewage. Can also be used in field treatment and recycling of domestic sewage from residential area and industrial organic sewage.    ADVANTAGE - Provides high loading capacity and suited for wide range of applications at low building and running costs, since the system does not use special soil.    DETAILED DESCRIPTION - The composite system has a cover layer (31), a diffusion water-ventilating broken stone layer (32), an upper anti-plugging layer (35), a ventilating broken stone layer (33), a lower anti-plugging layer (36), an artificial soil layer (37) and a water collecting and discharging layer (34) from the top down. A diffusion water-ventilating pipe network (41) is embedded in the diffusion water-ventilating broken stone layer. A ventilating pipe network (42) is embedded in the ventilating broken stone layer. A water collecting and discharging pipe network (43) is embedded in the water collecting and discharging layer. Seepage gravel (38) is placed between bottom of the diffusion water-ventilating broken stone layer and top of the ventilating broken stone layer. The cover land is preferably in form of green land, dry land, mantle rock, or hardened ground. The seepage gravel is located at the bottom of the diffusion water ventilating broken stone layer and passes through the upper anti-plugging layer in the central line position among the wall of the system and every two parallel diffusion water ventilating pipes to connect with the ventilating broken stone layer. Both broken stone layers are made of broken stones with grain size of 1 to 3 centimeters.    DESCRIPTION OF DRAWING(S) - The drawing shows the sectional view of a composite system.    Cover layer (31)    Diffusion water-ventilating broken stone layer (32)    Ventilating broken stone layer (33)    Water collecting and discharging layer (34)    Upper anti-plugging layer (35)    Lower anti-plugging layer (36)    Artificial soil layer (37)    Seepage gravel (38)    Diffusion water-ventilating pipe network (41)    Ventilating pipe network (42)    Water collecting and discharging pipe network (43)