The characteristics of the equivalent load of an arc suppression inverter are analyzed. The results show that the equivalent load is active load and the equivalent source has large amplitude and a wide range of variation. With the change of transition resistance and fault distance, the equivalent load impedance can show resistance, resistance inductance and resistance capacitance. This result shows that the inverter needs to be able to track the given current containing multiple frequencies stably under the condition of load property change and equivalent power disturbance. The improvement of anti-interference and tracking requirements increases the design difficulty. In view of this, the design method of output filter and controller for an arc-suppression inverter is proposed. The output filter is designed by the filter capacitor shunt method to ensure that the inverter can output current containing multiple frequencies. Capacitor series resistance is used to suppress the resonance instability problem caused by resistance-inductance load, and the calculation method of series resistance is given. The controller adopts the fixed bandwidth design method, and the bandwidth is selected in the amplitude-frequency characteristic overlap section. The design criterion of controller parameters is to ensure that the amplitude frequency characteristic of the transfer function has high gain in the low frequency band in the condition of resistance capacitance load. The correctness of the conclusion and the feasibility of the proposed design method are verified by PSCAD/EMTDC simulation. This work is supported by the National Natural Science Foundation of China (No. 61963014).