In order to improve the capacity of the air transportation in Taipei Flight Information Region (FIR), the use of the Global Position System (GPS) is proposed as a solution to meet the future need of air transportation within this region. For civil aviation applications, GPS must meet the Required Navigation Performance (RNP) in terms of the four requirements: accuracy, integrity, continuity and availability. Unfortunately, GPS alone cannot reach the RNP to ensure the safety of civil aviation users due to the lack of real time monitoring mechanism. To solve this problem, International Civil Aviation Organization (ICAO) and aviation organizations around the world developed the augmentation system to improve the GPS performance. One such system is the Ground Based Augmentation System (GBAS) which enhances GPS service to support aircraft approach and landing within one airport vicinity. In this paper, a GBAS ground facility prototype, called Integrity Monitor Test-bed (IMT), is developed to facilitate the implementation and operation of GBAS in Taipei FIR. The implementation of the IMT consists of three IMT reference stations and one IMT master station. The reference stations collect the signals from all the in view GPS satellites. The master station processes the data from the reference stations to generate the scalar corrections messages for the users. The corrections are subsequently examined by the above integrity monitoring process to ensure whether or not the users apply the broadcasted corrections to enhance their navigation performance. To evaluate the performance of the IMT, the Vertical Protection Level (VPL) is calculated and is presented on the Stanford Chart according to the requirements of the intended flight phase. In conclusion, the implemented IMT detects the anomalies of GPS satellites and receivers, and the results demonstrate the aviation navigation performance of the IMT within Taipei FIR. The analysis of the IMT results provides the valuable reference for the future implementation and operation of the GBAS in Taipei FIR.