Abstract: The coordinate of the GEO（Geostationary Earth Orbits） satellite is important in the algorithm of Beidou passive timing.The coordinate must be calculated quickly and exactly，in order to get the result of timing precisely.Considering the deficiency of Lagrange method to get the GEO satellite ephemeris，the algorithm about fitting the GEO satellite ephemeris with the Chebyshev polynomial approximation is adopted in the paper.The precise and the speed of the algorithm are improved，in the meantime，the time and space spent on memory storage also decreased greatly.In the practical test，the algorithm shows excellent performance，and it will play a significant role in the development of the Beidou navigation and location system in China.

Key words: Beidou, passive timing, ephemeris, Chebyshev polynomial

摘要： GEO卫星的坐标是北斗无源授时解算过程中一项重要的参数。为了精确地解算出所需时刻的授时结果，GEO卫星的坐标必须要快速而准确地计算出来。论文针对拉格朗日插值算法计算GEO卫星星历的不足，采用基于切比雪夫多项式拟合GEO 卫星星历求解算法。该算法提高了计算星历的精度和速度，同时大大降低了对内存的占用。该算法在实测中表现出了优良的性能，对我国北斗导航定位系统的后续发展具有重要的指导意义。

关键词: 北斗, 无源授时, 卫星星历, 切比雪夫多项式