Negative feedback hydraulic systems and rotary drilling rig

The present invention discloses a system and a feedback hydraulic rotary drilling rig. The above-described negative feedback hydraulic system comprising: a first main pump, the second main pump, the first main valve and second main valve, relief valve, the actuator, a pilot valve and a pilot pump handle; further comprising: a switching valve and a pilot change valve; pilot pump discharge port through the switching valve connected to the pilot valve of the pilot end; hydraulic control valve disposed in the oil path between the pilot valve and the second main valve handle, which comprises two working state; in the first operating state, the pilot valve of the first handle and the second operating oil port through the hydraulic control valve ports are in communication with a first end and a second pilot of the second end of the main hydraulic control valve ; in the second operating state, the pilot valve cutting off the pilot oil passage between the main valve and the second valve handle, and the first pilot hydraulic pilot end and a second end of the second main valve is equal to . The hydraulic system has a negative feedback system abnormal condition of low energy loss, high operating reliability advantages.