An omni-directional mobile microrobot for microassembly in a microfactory was presented.The microrobot was less than one cubic centimeter in size,and was driven by four electromagnetic micromotors with 3 mm diameter.The two important aspects for the microrobot precision,the structure design and control methods were analyzed.The structure design included the transmission system and the wheel fabrication and the control methods included the path planning and electromagnetic micromotor.In order to eliminate the drawbacks of microrobot structure,several novel control methods and ideas including the path planning and micromotor control were introduced.This path planning method was designed to solve the nonlinear problem of the microrobot during translational movement.Moreover,according to the structure constraint of the electromagnetic micromotor,the vector synthesis control of the torque was presented and the torque self-balance characteristic was utilized to improve the microrobot precision.Experimental results show that the microrobot can achieve 0.07 mm/step during translation,and 0.83 °/step during steering,which is three times that of the common control method.The microassembly experiments demonstrate the validity of these microrobot control methods,which shows the microrobot can satisfy the application requirements of microassembly.