Bypass valve by valve body, valve cover, valve core and spring parts, such as the sliding in the valve set pressure under the action of valve core, valve core movement to change the flow of the liquid, by-pass valve with by-pass and shutting down two states: on, in the process of drilling operation, valve cover and the hole is not closed and the valve body, bypass valve in the bypass state, mud around the motor in the drill string into the annulus;When the mud flow and pressure reach the standard set value, the spool moves down and the bypass valve hole is closed. At this time, the mud flows through the motor and converts the pressure energy into mechanical energy.When the mud flow value is too small or stop the pump, the spring will spool up, bypass valve hole in the open position – in the bypass state.