The high frequency and intensity of ionospheric activity in low-latitude regions pose a critical threat to the positioning accuracy， integrity， and service continuity of ground-based augmentation systems （GBAS）. Currently， ionospheric threat models and impact assessment systems for low-latitude regions are incomplete and insufficient to meet the operational needs of GBAS navigation in my country. Therefore， this paper innovatively constructs a low-latitude ionospheric threat model through long-term continuous observation of ionospheric activity at an airport in a low-latitude region， and systematically analyzes the GBAS operational errors and fault envelopes based on this model. This paper evaluates GBAS service performance through annual monitoring data， historical extreme ionospheric scenarios， and threat mitigation measures， and clarify the key impact patterns of ionospheric activity on GBAS. This provides targeted technical references for the construction of GBAS stations and the formulation of data processing standards in low-latitude regions of China， as well as both theoretical and engineering values.