A rotary power head is a key component of the cutting drill. In this paper, first, we researched the current situation of the rotary power head; Second, we proposed a new retard device called higher-order elliptic end surface movable tooth transmission, and then designed a new rotary power head based on this device. The moving parts in the transmission such as input and output shafts are self-balancing, so the transmission can achieve the random tooth difference. A rotary power head of a drill with this transmission has many advantages, such as convenient disassembly or loading, large transmission torque, small radial size and the suitability for heavy loads. Finally, 3D model based on Solidworks2010 was established.