Instruments for GI diagnostics are increasingly moving toward robotic capsule endoscopes because of their locomotion capabilities. This paper presents a wirelessly powered robotic capsule endoscope that can actively move in the small bowel exploiting the expanding-extending principle. After analyzing the demands of the locomotion, a novel radial motion mechanism with a large expanding/retracting radial ratio was designed, as was an axial motion mechanism with a compact structure. A control system with a special position detector to let the micro-motors avoiding stall state was developed to enhance the stability of the mechanism and reduce the robot's power requirements. The wireless power system enabled the robot to inspect the full length of the intestinal tract. The assembled micro-robot was 14 mm in diameter and 45 mm in length. The maximum anchoring diameter was 32 mm, and the axial telescopic length was 9.5 mm. The test results proved the feasibility of the robot.