WEDM (Wire Electrical Discharge Machining) is an effective method for machining micro gears. In this paper, aiming at WEDM characteristics, the gear design method is discussed. Based on gear meshing theory, the gear tooth profiles are generated. Mesh interference and wire path for WEDM algorithms are presented. Micro gear CAD/CAM software is developed whose functions include gear modeling, interference judgment and wire path generation. Finally a pair of micro gears is manufactured to verify the work in this paper. With the above method, the constraints on some gear parameters can be eliminated and the micro gear design is made more flexible.