As the grounding electrode of HVDC is in single electrode blocking condition, the large stray current into the ground may cause the electromagnetic valve misoperation risk, affecting the normal operation of the pipeline. The mathematical model of the influence of conducting interference on the solenoid valve coil is established, the mechanism of misoperation of electromagnetic valve caused by dc stray current is studied. By means of numerical simulation, a simulation model of grounding electrode interference to nearby pipelines in a 1 100 kV UHVDC transmission project in China was established, and a real-time data acquisition system of ground potential was designed. Simulation and field test results show that the dc interference of the electromagnetic valve in winter is 3. 43 times that in summer. The simulation results are basically consistent with the measured results, and the error is within 10%. After adding 4 and 6 insulated joints along the pipeline, the ground potential difference of the pipeline is reduced by 62. 1% and 71. 4%. In order to reliably prevent abnormal operation of electromagnetic valve, inspection of valve chamber should be strengthened in winter, and insulation joint should be installed along the pipeline upstream and downstream.