To evaluate the potential interference of grounding electrode in monopolar operation on buried oil and gas pipeline, a circuit simulation model considering cathodic protection system and polarization effect of the pipeline is established by using Beasy software. Through simulation calculation, the influence of different monopolar polarity, operating current of grounding electrode and distance away from the pipeline on the distribution of polarization potential of pipeline is studied. The results shows that the higher the operating current is, the greater the polarization potential shifts. The linear relationship between the operating current and polarization potential is found out that the closer the grounding electrode is to the pipeline, the shorter the pipeline span under severe interference is at the near end of the grounding electrode, and meantime, the greater the polarization potential shifts. The cathodic protection system of the pipeline can suppress certain stray current generated by HVDC. For real conditions, the suppressing effect of the cathodic protection system should be considered to evaluate HVDC interference on the pipeline.