Abstract: The robust design optimization of the needle bar mechanism in computerized embroidery machine is achieved. Firstly, the calculation of the equivalent length of planar linkage mechanisms with revolute-joint clearance is modeled and the calculating formula of equivalent length is derived. When the length error of component and kinematical pair clearance are taken into account, the mathematical model for the robust design optimization of needle driving mechanism is then established to minimize the error and the standard deviation of needle bar position. The mathematical model is solved and its solution shows that the robustness of the needle bar position of needle driving mechanism is observably improved without increasing the cost of manufacture.