The invention relates to a tool special for demounting a barometer in a 10 KV ring main unit and a method and belongs to the technical field related to power equipment. The tool mainly comprises a force application handle, wherein the force application handle is fixedly connected with a plurality of connecting rods through a middle rod, and the other ends of the connecting rods are fixedly connected with torsion sleeves which are provided with opening structures. By the arrangement of a novel structure, the tool can be used for directly demounting the barometer in the ring main unit, and interference with other elements and devices hardly occurs in the demounting process.