Abstract: Regarding the synchronous decline in the two sets of geo-resistivity observation systems at Nanjing station on January 9, 2023, we checked the condition of the observation system, investigated the natural and site environmental factors, as well as conducted multi-scale and multi-item joint analysis in time and space. The results show that this anomaly is affected by the construction of high-voltage transmission lines rather than earthquake precursor anomaly, and the explanation was provided for the abnormal mechanism. The process of analysis and determination of interference has a great reference value for verifying the causes of abnormal changes in geo-resistivity data, and also provides a train of thought for the analysis and interpretation of geo-resistivity abnormal data.