The present invention has disclosed a power head of a rotary drilling rig and a rotary drilling rig. The power head comprises a driving device, and a transmission device including an input shaft operatively connected with the driving device, a first output shaft operatively connected with a drilling rod of said rotary drilling rig and a second output shaft operatively connected with a casing driver of said rotary drilling rig, wherein the second output shaft has a first state, in which an output torque that of said second output shaft is greater than that of said first output shaft when said driving device drives said input shaft to rotate. When it is necessary to perform a full casing embedment, the power head may be manipulated to make the second output shaft be in the first state to output an output torque for driving the casing driver greater than an output torque for driving a drilling rod, so that a casing may be smoothly embedded by utilizing a built-in function of the rotary drilling rig, and a high construction efficiency can be achieved.
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