The 3D micro-mold which is fabricated by the femtosecond laser cutting and micro electric resistance slip welding is formed through the lamination of multilayer 2D microstructures. By using this technology, the 3D micro-mold with a high depth-width ratio can be manufactured. In order to improve the laminated precision and joining strength of each layer of 2D microstructure, this research applied layer-by-layer micro electric resistance slip welding to weld each layer of 2D microstructure. Firstly, the proper technical parameters were obtained through the experiments of layer-by-layer micro electric resistance slip welding. Secondly, through the layer-by-layer micro electric resistance slip welding, multilayer 2D microstructures were weld together and a 3D micro-mold was formed. Moreover, the anti-shear stress test of 3D micro-mold was done. In the layer-by-layer slip welding process, electrode could produce some losses and the losses could deposit on the surface of micro-mold. This research also studied the deposition effect of the electrode. Finally, based on the above studies, the micro square-hole array and the micro-gear cavity were fabricated by joining multilayer 2D microstructure.