A structure of signal line comprising a core portion, a middle filler layer, an obscuring layer and a coating portion, the core portion is a transmission conductor with a rectangular cross section; the obscuring layer has at least a knitted metallic obscuring layer; the coating portion has at least a layer made of polyvinyl chloride composition; and the middle filler layer is comprised of a plurality of hollow tubes. The core portion is tangled with the middle filler layer to make the line stronger in addition to being flexible, so that the line will not have the core portion damaged when it is bent to deform, plus the obscuring function of the obscuring layer, the interference among a magnetic field, radio frequencies and static electricity can be reduced, thereby, attenuation rate of the line can be reduced, distortion of the line can be smaller, and high quality of the line can be obtained.