To compact and miniaturize the high-power microwave system and reduce the energy consumption of the magnet system, the superconducting magnet which generates the guiding magnetic field is studied and designed. The magnet is composed of rare earth barium copper oxide coil pancakes. In the cryogenic system, four air-cooled Stirling cryocoolers are used to cool down the superconducting magnet. To be suitable for vehicle environments and reduce the heat leakage, a new cone bearing structure of non-metallic material is adopted as the load-bearing structure of the magnet. And the load-bearing situation of the magnet structure under the general vehicle environment is analyzed by the simulation. The superconducting magnetic field in the uniform region reaches 4 T when the current is 77.49 A in the range of 40-50 K. The energy consumption of the whole system is 80% lower than the traditional technology. The experimental results show that the upper temperature limit of the high temperature superconducting magnet (HTS) is 48.9 K.