Truck-mounted drilling rig and power head thereof

The utility model discloses a power head of a truck-mounted drilling rig. The power head comprises a drill rod clamping portion and four motors driving the drill rod clamping portion to rotate, the drill rod clamping portion clamps a drill rod of the truck-mounted drilling rig, and the motors are arranged on two opposite sides of a drill rod mounting axis in pairs and are all in gear connection with the drill rod clamping portion so as to drive the drill rod clamping portion to rotate synchronously. The power head acquires more torque by increasing the motors and arranging the positions of the motors correspondingly without being limited to motor displacement, larger total displacement can be acquired through the motors even if one single motor lacks displacement, mutual promotion of acting forces provided by the motors is achieved, loss caused by unstable transmission is avoided, and utilized utilization of drilling power is befitted highly; in addition, the added motors and the original motors are all in gear connection with the drill rod clamping portion without increasing the height of the power head or center distance from a drill rod to a mast, and complete truck stability is unaffected after the power head is mounted to the truck-mounted drilling rig.