The correlation between harmonics of converter stations and operation mode of main plants near the converter station is analyzed.The fluctuation of AC-side fifth-order harmonics and DC-side sixth-order harmonics and the action principle of DC filter capacitor's overload protection alarm are analyzed.By analyzing the on-site harmonic monitoring data and the change of the operation mode of near-zone important plant,the emergent handling strategy for harmonic monito-ring and DC filter capacitor overload protection alarm is proposed.The proposed measures has been verified effective in im-proving DC harmonic disposal capability and safe and stable operation level of HVDC systems.