Hydraulic nut assembly

A hydraulic nut is provided to improve the sealing effect of a cylinder by closing a lib part to a wall after being transformed with the fluid pressure. A hydraulic nut comprises an inner body(1), an outer body(2), an inner and an outer sealing material(4a,4b), a ring cylinder, a flow path(10), and a lock nut(3). The inner and outer sealing material comprises the sealing surface. The sealing surface is made of metal. The sealing surface is contacted with the fluid. The sealing surface comprises a lib part. The lib part comprises inclines inclined while facing each other based on a center groove.