Nowadays with the developing augmentation system or regional satellite systems, the performance of GNSS for civil users is extremely improved especially on the error budget from system characteristics. However, unpredictable factors on the ground user environment, such as intentional or unintentional interferences, strongly degrade the performance of GNSS receiver. It is a significant issue to monitor and investigate the interference effect while applying GNSS for safety of life applications, aviation applications especially. In this study, a low-cost GPS interference monitoring system was deployed at a civil airport for the long-term interference monitoring, and so far several interference events were observed during this period. This paper focused on the reorganization of what the interference observed is, and identifications of the interference characteristics and the influence on navigation service. The Fourier-sine-spectrum-based time-frequency method analyzed the recorded intermediate frequency signal to speculate the interference statistics such as the period, the duration, the frequency of occurrence, and so on. In addition, the interference influence was evaluated on the criterion of the positioning results and the estimated Carrier-to-Noise ratio (C/N0) in GNSS signal tracking process. In summary, this paper offers the possibility to find useful information of these interference events for the airport environment in locating jammers or mitigating the effects of interference signals.