The structure and control system of micro robot fish are designed based on the properties of the IPMC (ionic polymer metal composite) after analyzing locomotion and force of small fish. Then efficiency improvement of the IPMC is discussed, and various locomotion patterns are realized on the micro robot fish. The experimental results prove that an IPMC based centimeter scale micro robot fish is feasible. The velocity control can be realized by changing frequency and duty ratio of the control signal, and ascent-descent, turning, cruising can be realized by the cooperation of pectoral fin and caudal fin. Finally, this paper analyzes how to improve propulsive efficiency from the viewpoint of structure design of the caudal fin propulsor.