Abstract
The rational formula and structure formula of robots were proposed. The axis direction of the motor which composes a robot is classified by Roll axis, Pitch axis and Yaw axis. When there is a motor on the body side, the initial of axis is written with a capital letter, and written with a small letter in case of opposition. The whole structure of the robot is expressed as a rational formula of the robot to show molecule structure in chemistry. SANSYRO n is expressed as a rational formula of the robot with "Humamoid-16DOF=Head-Y-(Arm=Pr-0-0)_2-Y-(Leg=RP-p-PR)_2". Human structure is analyzed, and it is described about the way of developing humanoid.