To provide a coupling structure of a thermal fuse of a rivet joining system.

By rivet joining mainly thermally fusing metal to two separated terminals in a circuit, the two terminals are electrically connected to communicate the circuit. At a state without external force added, the two free ends of the two-piece terminals retain a constant interval. When a current is overloaded, the circuit is overheated, or an environment temperature in use is too high, the thermally fusing metal receives heat to have its temperature rise and fuse and fracture. With this, the free ends of the two-piece terminals are out of contact with each other to have the circuit in an OFF state.