The invention discloses a thermal cutting tool for a cable sheath. The thermal cutting tool comprises an electro-thermal type steel cutter knife and a heating power supply plug therefor, a U-shaped knife rest and a supporting wheel; the electro-thermal type steel cutter knife is a C-shaped cutter with an insulating sleeve in the internal part; an integrated insulating plate is arranged on the periphery of the insulating sleeve; the insulating sleeve is embedded in the C-shaped cutter; pin holes are formed in the C-shaped cutter parts on the two sides of the insulating plate; the pin holes are adaptive with the heating power supply plug; the electro-thermal type steel cutter knife is mounted on the inner wall of the left side of the U-shaped knife rest through a left bracket equipped with a rotary shaft; the supporting wheel is mounted on the inner wall of the right side of the U-shaped knife rest through a right bracket equipped with a rotary shaft; and the center of the C-shaped cutter and the center of the supporting wheel are on the same horizontal line. The thermal cutting tool is simple in structure, convenient and rapid to use, and capable of rapidly removing rubber or plastic sheaths of rubbers, preventing from damaging metal wires in the cables, reducing labor intensity and improving cable construction efficiency, so that the thermal cutting tool is suitable for the cables of multiple specifications.