The invention relates to a high-density fish-and-vegetable symbiosis system which comprises a sewage tank, a support, a drainage main pipe, a fish tank, a cultivation tank, a sewage pump, a circulation pipeline, a water distributor, a cultivation tank water inlet pipe, a sewage pipe water outlet pipe, a clear water drainage pipe, a water distributor water inlet pipe, a central outer pipe and a central inner pipe. The fish tank is composed of an upper cylinder and a lower inverted cone. The center of the bottom of the inverted cone is provided with a groove, the central outer pipe is mounted inthe groove, the central inner pipe is mounted in the central outer pipe and passes through the bottom of the fish tank and is connected with the drainage main pipe at the bottom of the fish tank, thedrainage main pipe is connected with a sewage drain pipe and a clear water drain pipe respectively through a three-way valve, the sewage drain pipe is disposed above the sewage tank, the pipe wall ofthe central outer pipe is provided with a plurality of holes, the holes are covered with a grid, and the height of the central inner pipe is lower than that of the central outer pipe. The system is simple, convenient to operate and low in running and maintenance cost, the quality of treated water is good, the breeding density is large, and the planting yield is high.