Polyculture system and polyculture method of fish and mussel in fresh water pond

The invention discloses a polyculture system and polyculture method of fish and mussel in a fresh water pond. The polyculture system comprises a polyculture pond, wherein the polyculture pond is divided and isolated by an isolation device into a fish intensive culture region and a fish and mussel polyculture region, cultured fish and mussel can not pass through the isolation device, but microorganisms and suspended particles in the water can permeate the isolation device so as to be freely exchanged between the regions; in the whole polyculture pond, the number ratio of fish to pearl mussel is 1:(0.5-1.25); mixed feed is fed into the fish intensive culture region at a fixed point by a bait feeding machine, oxygen is increased in the fish intensive culture region by an oxygen-increasing machine so as to promote the substance exchange between the fish intensive culture region and the fish and mussel polyculture region, the color and transparancy of water in the polyculture pond are adjusted by fertilizing, and