The invention relates to a heat dissipation device in an electrical cabinet. The heat dissipation device comprises a fixing pipe, a connecting pipe, a heat dissipation ball, and a gas circulation pipeline. The top end of the fixing pipe is fixedly connected with the top plate in the electrical cabinet, and a clapboard is disposed in the connecting pipe. The bottom plate of the bottom part of the connecting pipe is uniformly provided with air vent holes, and the heat dissipation ball comprises 3-20 arc-shaped heat dissipation pipes. The heat dissipation pipes are provided with heat dissipation holes, and the bottom parts of the heat dissipation pipes in the heat dissipation ball are merged together. The gas circulation pipeline comprises an air exhaust pipe, an air pump, and an air feeding pipe. The connecting pipe is provided with a connecting pipe adjusting device, which comprises a cabinet fixing plate, a first connecting rod, a second connecting rod, a third connecting rod, and a spring. The heat dissipation device has advantages of good heat dissipation effect, simple and flexible structure.