Abstract: A new micro robot inside human body driven by exterior rotating magnetic field is proposed.It takes a cylindrical NdFeB multipole permanent magnet composed of several neighboring tegular magnets magnetized anisotropically along radial direction as exterior actuator,and a magnet with the same structure embedded inside the robot body as the inner actuator.The robot screws forward inside pipe under the action between spiral rib on the exterior surface of robot body and fluid dynamic pressure when robot rotates by magnetic torque,which is generated by magneto-mechanical coupling from rotating exterior actuator to inner one.Based on a newly developed swimming mathematical model,its characteristics of omni-directional drive is studied in the environment of erect pipe.Experimental results show that the robot can realize omni-directional drive.