Before the steam turbine is started, the pulse oil circuit shall have no oil pressure, the pressure transducer slide valve, the pilot valve slide valve and the slide valve of the starting valve shall be in the lowest position under the action of spring force, the synchronizer should return to the lower limit position. When the high pressure electric pump or steam -operating oil pump starts, the pressure oil is divided into two circuit via the non-return valve: One circuit enters to the bottom of the high pressure pilot valve via the starting valve, the slide valve of the pilot valve moves up, the pressure oil enters to the lower part of high pressure oil servo motor, close the high pressure regulating valve. The other circuit enters to the main steam operating seat oil cylinder and extraction non-return valve oil cylinder via the axial displacement breaker, emergency throttle and magnetic breaking throttle. Open the main steam to start the unit. When the rotating speed increases, the oil pressure at the main oil pump outlet reaches the specified value, the electric oil pump or steam-driving oil pump automatically stops working. When the rotating speed rises to make the regulator act, the regulator starts acting.