Abstract: A millimeter-scale mobile microrobot with a novel omnidirectional structure for microassembly in a microfactory is presented,and it is driven by four electromagnetic micromotors with 3 mm in diameter and equipped with a pair of micro-grippers.The rank of the kinematic matrix is analyzed to demonstrate the microrobot's omnidirectional characteristics,and the kinematic equation is set up for the micro-gripper.A microrobot control system is designed based on computer vision,and the microrobot locating and driving approaches are described.Experimental results demonstrate the load-carrying ability and maneuverability of the microrobot,and the validity of the control system.