The invention belongs to the technical field of electrical protection devices, and relates to a built-in fsp thermal fuse. The main structure includes an upper lead rod, a wiring sleeve, a thermal fuse, a lower lead rod, a protective sleeve, a terminal and a drill hole. One end of the upper lead rod and one end of the lower lead rod are integrally fixed with a wiring sleeve, and the inside of the wiring sleeve is hollowed out with cylindrical boreholes. The terminals on both ends of the fsp thermal fuse are respectively fixedly sleeved with the wiring sleeves on the upper lead rod and the lower lead rod. A protective cover with an integral hollow structure is fixed at the socket of the terminal and the terminal sleeve to prevent sparks and arcs when the thermal fuse is blown. The fuse is simple in structure, reliable in principle, scientific in design, convenient to use, versatile, low in manufacturing cost, and environmentally friendly.