The invention discloses a safety valve, which comprises a valve body and a liquid inlet joint, wherein the liquid inlet joint is provided with a liquid inlet hole; the safety valve also comprises a valve core assembly which is movable, is arranged in the valve body and is further used for controlling the opening and the closing of the liquid inlet hole; the valve body is provided with a liquid discharge hole; the valve core assembly comprises a sliding seat, a threaded sleeve which is arranged in the sliding seat, and a valve pad which is arranged in the threaded sleeve; the valve pad has a sunk structure. According to the safety valve which is provided by the invention, by arranging the movable valve core assembly inside a valve casing, the valve core assembly can be used for controlling the on-off of an oil way from the liquid inlet hole to the liquid discharge hole; after the valve core assembly is far away from the liquid inlet joint, the large-flow overflow can be realized; the flow of the safety valve is greatly improved; the axial displacement of the valve core assembly can be shortened through short-time quick overflow; the axial deformation of a reset spring can be reduced through the shortening of the axial displacement of the valve core assembly; pressure fluctuation can be decreased finally.