Rotary drilling rig and hydraulic rotation system thereof

The invention relates to the technical field of piling machinery and discloses a rotary drilling rig and a hydraulic rotation system thereof. The rotation hydraulic system comprises a main reversing valve, a rotation motor, a first oilway, a second oilway and a third oilway. Two working oil ports of the main reversing valve are connected to two working oil ports of the rotation motor via the first oilway and the second oilway, when the first oilway is at oil inlet state, the rotation motor drives a rotation bearing to rotate forwardly, and when the second oilway is at oil inlet state, the rotation motor drives the rotation bearing to rotate reversely. An oil inlet end of the third oilway is connected with a forward-rotation pressure oilway of a power head, and an oil outlet end of the third oilway is connected to the second oilway. In the hydraulic rotation system for the rotary drilling rig in the embodiment, braking torque of the rotation bearing is improved and rotation failure is avoided. Further, in the hydraulic rotation system, braking capability of the rotation bearing at any position can be improved without a self-made chassis.