As an emerging technology in the field of civil aviation, Ground-Based Augmentation System (GBAS) can provide Category-I or higher precision approaches and landing guidance services for aircraft. Ionospheric activity is one of the important factors affecting the performance assessment of GBAS, so ionospheric activity needs to be monitored and evaluated. Based on the Time-Step method, this paper uses the actual received dual-frequency GPS data to conduct long-term monitoring of ionospheric activities at Xianyang Airport, and conducts simulation evaluation of GBAS service performance during the monitoring period. The results indicate that during the monitoring period, the ionospheric activity at at Xianyang Airport is low, and the service performance of GBAS is not affected by the ionosphere, which can meet the performance requirements of Category-I precision approaches.