Abstract: This paper presents a new method for orientation determining, which can determine the baseline＇s orientation with only one geostationary satellite. The method depends on the fact that the satellite can be considered to be stationary relative to the observer on the earth. Because of the nature of the satellite, the line-of-sight vector from observer to satellite is also invariable, Its azimuth can be obtained through the coordinates of the satellite and the observer. If the baseline is in motions, the difference carrier phase between the two antennas will be changed accordingly. According to the variety, the angle between the baseline vector and the line-of-sight can be figured out. Since the line-of-sight is known, the azimuth of the baseline vector can be obtained easily. In this paper the error of the method is analyzed by mathematical and emulational ways, It comes to a conclusion that the best precision of the orientation can be obtained when the baseline is perpendicular to the sight line of the satellite. At the end of this paper the experiment is accomplished with a Beidou satellite. The experiment result shows that the precision of the baseline＇s orientation could be better than 0.07° when the baseline length is about 0,827 meters long; So it is proved that the principle of orientation determining with single geostationary satellite is right and feasible.