The digital construction of Taiyuan geomagnetic observatory has been completed during the tenth five-year plan, but the observing data have a high level background noise which has impacted the data using. After carefully analysis by several technical measures, several interference factors have been discovered. The power supplied during the observation of the geoelectrical resistivity is the main reason. There are also some other factors contribute to the high level background noise. The detail analyses are presented and the methods to avoid or eliminate these interferences on the observation data also have been proposed in the paper.