This study investigates the impact of geomagnetic storms on GNSS positioning accuracy by analyzing variations in the Dst index and GNSS positioning data. By comparing positioning deviations during storm and non-storm periods, the research assesses the influence of solar activity-induced disturbances on GNSS precision. Geomagnetic storms disrupt the Earth's magnetosphere, causing ionospheric disturbances that affect GNSS signal propagation and positioning. The study analyzes the pseudorange measurement and ionospheric-free models of GNSS systems using Dst index data collected during enhanced geomagnetic activity, examining changes in positioning metrics during storm and non-storm periods. The results indicated an increased deviation during geomagnetic storms, with positioning deviations reaching −8.390 m in the E direction and −7.781 m in the U direction when the geomagnetic storm's Dst index peaked at approximately −130. These deviations were significantly higher than the errors observed during periods of stable geomagnetic activity, which were on the order of meters, confirming the impact on GNSS positioning. However, the use of systems without an ionospheric model can mitigate this interference to some extent. This study provides valuable insights for the future development of GNSS monitoring systems.