In the difference and integrity monitoring algorithm of the ground-based augment system, pseudo-range difference is a commonly used measurement difference mode, it can effectively eliminate most of the spatial and timely correlation error in the case of short baseline, thus can effectively improve the positioning accuracy of the airborne terminal. And in its integrity algorithm, the selection of statistical threshold is a very important aspect and the value of quantile a which corresponding false alarm rate in the threshold calculation formula directly determines whether the result of the differential positioning is good or bad. This paper based on conducting data analysis through collecting a large amount of integrity statistics data in GBAS ground station of differential satellite, then through analyzing the threshold of the integrity statistics data and comparing the results of the pseudo-range differential positioning by steps “2σ”, finally verifies the rightfulness of using “6-sigma” as selecting the threshold of the integrity statistics data