The invention relates to a multi-pair bi-layer folding flat wire, a synchronous extruding device and an extruding method of the multi-pair bi-layer folding flat wire. The extruding device comprises a core wire paying off device, a pass line parallel guide rod, a flat wire extruder, a cooling device, a detection device and a winding up device which are sequentially distributed according to production processes. The extruding method includes steps of leading out a plurality of core wires from the core wire paying off device, passing the core wires through the pass line parallel guide rod to enter the flat wire extruder, subjecting the core wires to extrusion forming to form the multi-pair bi-layer folding flat wire by means of an extruding mold of the flat wire extruder, cooling and detecting the flat wire, and winding up the flat wire in the flat wire winding up device. By means of the extruding device and the extruding method, the multi-pair bi-layer folding flat wire can be extruded in one time, so that production efficiencies are substantially improved, electrical performances of cables are stable, and qualities are greatly improved.