A second-level magnetic field system based on storage supercapacitor is designed to fulfill guiding magnetic field requirement in High Power Microwave(HPM) source field. Firstly, basic principles and calculation methods on super capacitor magnetic field system are briefly introduced. Then the excitation source and corresponding solenoid are discussed in detail. Through simulation and experiment, it is verified that the magnetic field system based on supercapacitor storage could well meet the needs of HPM magnetic field. Finally, the bottleneck and outlook of this kind of magnetic field are analyzed generally.