At the beginning of a Fourth Industrial Revolution, the robotics is more important among the other technologies. The robots which have high performances including high speed, high power at low speed with in a small-occupied volume are required in various fields. These criteria aimed to increase the performance of four-legged robots. In this paper, the high speed and power actuator is proposed because the actuator of robotic system determines its performance. To design the high speed and power actuator, the design variables are selected through the mechanical and electrical elements. Based on the design variables, the optimization model of actuator is presented through performance analysis.