The invention discloses a water treatment system for internal-circulation running-water cultivation in a pond. The water treatment system comprises a purification area (1), ecological islands (2), a breeding water tank (3), an aeration and water pushing area (4), a sewage collecting and drainage area (5), a working platform (6) and a pond (8). The long-strip-shaped ecological islands which are distributed in a staggered mode are arranged in the purification area, and aquatic plants are planted on the upper surfaces of the ecological islands and on the shallow water areas of side slopes of theecological islands, so that on one hand, water can be purified, on the other hand, water discharged from the breeding water tank can only flow along an "S-shaped" water path, a situation that the sewage is not fully purified and directly flows into the breeding water tank in a mode of "cutting a corner" is avoided, and meanwhile, a situation that dead water areas appear in a part of regions in thepond is avoided. The ecological islands are mainly prepared by piling the bottom mud of the pond, so that construction cost is low, the volume of the pond cannot be reduced, and shallow water areas and deep water areas can also be formed in the purification area, wherein the shallow water areas are beneficial to growth of aquatic plants, and the deep water areas can prevent water temperature frombeing too high in summer. Therefore, functions of purification areas of the pond can be enhanced, and the water purification effect can be improved.