Recent researches in the robotics have been directed to the interaction between humans and robots, similarly to the relationship between humans and animals. We developed the interactive emotional robot, ´RAI´ that can adapted to the human living environments. This paper presents the mechanism design and dynamic analysis of the newly-developed robot considering its emotional meanings and operations. The two-wheeled inverted pendulum type mechanism is selected to this robot system, because it can improve the mobility as lower curve radius and make the innate clumsy monoaxial motion while controlling it. This robot can move freely in a with the help of various sensors including gyro.