The invention discloses a cofferdam device capable of resisting to high wind waves and intercepting bloom-forming cyanobacteria. The cofferdam device comprises foam floating bodies, wrapping cloth, skirt curtains and reinforcing bands, rubber wrapping cloth is used as the floating body wrapping cloth outside the floating bodies, the skirt curtains are reserved on the underside of the floating body wrapping cloth, a nylon strap or rope serving as one reinforcing band is arranged in the middle of each skirt curtain, every two reinforcing bands are connected by a metal hook connector, an iron chain is arranged at the lower end of each skirt curtain, the joints of two ends of each cofferdam are fixed by steel plates, two rows of holes are punched in each steel plate, the nylon ropes penetrate into the holes for connection, then the metal hook connectors on the reinforcing bands are used for connecting the two ends, each cofferdam is connected with iron anchors at the two connectors by anchor lines, the iron anchors are thrown into a lakebed, and the anchor lines on the iron anchors are integrally connected with each cofferdam. The cofferdam device is simple in structure, easy and simple to operate, high in efficiency of capturing the bloom-forming cyanobacteria and low in cost, water cofferdams are high in wind-wave-resisting capability, good in stability, convenient to operate and suitable for being arranged underwater for a long term, and the problem of mass cyanobacterial bloom accumulation in bloom-forming cyanobacteria harvest is solved.