Abstract: The external alternating longitudinal magnetic field can effectively improve the transition form of high current GMAW droplets and improve the stability of the welding process. In actual tests, it is found that when the frequency of the alternating current given by the power supply is relatively high, the excitation current waveform is distorted and its effective value is reduced. Using the principle of RLC series resonance, the frequency range of 2000-5000 Hz was divided into three sections, each section was set with a typical frequency, the load tank parameters at the three typical frequencies were designed respectively, and Simulik simulation software was used to verify the designed parameters. The actual experimental results show that the circuit achieves resonance at the set typical frequencies, and the effective value of the current in the corresponding frequency range is improved compared with that without the resonance compensation capacitor.