CMC-2B air-insulated bus duct is made by improved processing on the basis of air-type bus duct. The busbar conductor is made of electrolytic copper with a copper content of more than 99,99%. After high-quality processing, the outer surface is wound with a polyester insulating film, and then shrinked with a PVC heat-shrinkable tube, which significantly enhances the insulation performance of the copper busbar. The phases and shells are separated by flame-retardant insulating blocks, and then assembled in a closed and well-grounded metal shell, the electrical and mechanical properties are very stable. The shell is processed and formed by high-quality cold-rolled plates, and the surface is treated with electrostatic spray, which greatly improves the corrosion resistance.