The invention discloses a thermal shrinkage and cold expansion type self-on-off cable sheath, and belongs to the field of cables. According to the thermal shrinkage and cold expansion type self-on-offcable sheath, through arranging a thermal shrinkage and cold expansion mechanism, when external temperature is high, a transverse temperature sensing rod is heated to expand, the upper ends of the two thermal shrinkage cold expansion plates are close to each other and are in a thermal shrinkage state. At the moment, the self-on-off heat-conducting rod is contacted with the heat-conducting block,the heat is dissipated to the outside of the outer sheath along the self-on-off heat conduction rod. Compared with the prior art, heat is directly dissipated from the heat conduction block to the outside of the outer sheath by taking air as a heat dissipation medium, the heat dissipation efficiency is obviously improved. When temperature is low in winter, the transverse temperature sensing rod shrinks, at the moment, the distance between the two thermal shrinkage and cold expansion plates is large, the two thermal shrinkage and cold expansion plates are in a cold expansion state, the self-on-off heat conduction rods do not make contact with the heat conduction blocks, heat at the heat conduction blocks is dissipated out of the outer protection layer through air serving as a medium, the heat dissipation efficiency is low, the temperature of the cable is effectively kept, and the normal power transmission efficiency at the low temperature is effectively guaranteed.