Based on the state equation method, an analytical calculation method for the DC loop harmonic impedance of the HVDC converter is established. MATLAB and PSCAD /EMTDC software are used to build model and simulate the DC harmonic impedance to verify the correctness of the proposed method. The typical frequency spectrum of the DC harmonic impedance of the converter is obtained. The coupling relationship between the DC harmonic impedance spectrum and the control parameters is analyzed, and the key control parameters that affect the DC harmonic impedance are extracted, and a DC loop harmonic impedance adjustment and DC resonance suppression method based on control parameter modulation is formed. The efficiency and flexibility of DC resonance suppression of the converter have been improved.