Based on the improvement of satellite navigation accuracy through differential positioning, GBAS adds a series of integrity processing algorithms to enable aircraft equipped with corresponding airborne equipment within the airspace covered by the airport to obtain precision approach and landing guidance services of CAT-I or even higher standards. In the construction planning stage of GBAS, site assessment is an important method to determine the performance of GBAS. The system composition and working principle of GBAS are introduced, focuses on the GBAS site assessment method, and GBAS site assessment with an airport actual measurement data is conducted as an example, which provides a technical basis for the subsequent application of GBAS.