Abstract: A transmission cable structure includes one or more propagation channels. Two insulated conductors in each of the propagation channels are joined to each other tightly as a single piece, a first cover and at least one drain wire disposed outside each of the propagation channels for location and shield, a second covering and a jacket enclosed outside the first cover and the drain wire for forming electrical shield. Therefore, the two insulated conductors joined to each other tightly can ensure the symmetry of the transmission signal, also can prevent noise effectively and the electromagnetic wave of different loops by the double shield spaces formed by the first covering and the second covering in the transmission cable, so as to improve the transmission quality of the electronic signal.