The invention relates to underwater robot technique, especially providing a hydraulic-shears, which is formed by a fixing anvil pin, a shearer, a movable shearing cutter, a drawing straight pin, a cylinder, and a piston rod. Wherein, said shearer is in U-shape whose one side is rectangle; the shearer has a horizontal groove guide rail and a cylinder hole at vertical direction; the fixing anvil pin through said cylinder hole is connected to the U-shape bottom edge; another side of U-shape is in post-structure connected with said cylinder; the inner part of post-structure is in chamber structure while a square hole is near the cylinder; the cutter has a groove guide rail through said horizontal direction mounted inside the chamber, to be through said square hole and connected with one end of piston rod via drawing straight pin; and the open of said U-shape structure of said shearer contains steel wire. The invention has simple structure, lower machining precision, non-cutting left of steel wire, smaller size, lighter weight, application of easily changing vulnerable parts, reliable operation and the application of operation unmanned remote-control diving apparatus.