This paper introduces the structure and characteristics of the power head, a major component of deep sea core sampler. According to the special conditions of deep sea drilling, a self-desertion mechanism and impact break-out mechanism are specially designed on the power head to abandon the sticking drill pipes in hole when they can not be withdrawn or to loose the drill pipe threads by compact when the power head torque hydraulic motor fails to unscrew drill pipe. This paper emphatically introduces the structures and working principles of drill pipe self-desertion mechanism and impact break-out mechanism.