The invention discloses a water, light and fish complementary comprehensive power generation system for a reservoir. The system comprises suspension type fish and light complementary generating stations arranged on the upstream of a hydropower station dam, pooling stations and a hydraulic booster station. The suspension type fish and light complementary generating stations, the pooling stations and the hydraulic booster station are all arranged away from a reservoir navigation and flood discharge river. The hydraulic booster station is connected with the pooling stations through corresponding power transmission lines. The suspension type fish and light complementary generating stations comprise connection bearing balance structures and fish and light complementary power generation structures. The connection bearing balance structures are arranged on both sides of the reservoir and on the water surface, and the fish and light complementary power generation structures are arranged on the connection bearing balance structures. By the adoption of the system, the water area condition of an existing water-power engineering reservoir area is fully utilized, various adverse effects such as water-level variation, large depth of water and flood discharge at the flood season of the reservoir are overcome, and two fundamental restriction problems that floor area is huge and power grid connection matching is incomplete in the photovoltaic power generation or fish and light complementary power generation technology can be well solved.