Abstract:In this paper,based on research from July 2014 to July 2015 from the International GNSS service (IGS) orbit combination theory, GPS combined orbit is computed by an independent algorithm, using the precise orbit of IGS analysis centers. This method has advantages over the combination method of GEO/IGSO/MEO orbit of the Beidou navigation system.According to the experiment, the maximum three-dimensional root mean square(RMS) accuracy difference of combined orbit is up to 4 mm, using the analysis of the Scripps Institution of Oceanography (SIO). The precision of the combined orbit increases nearly fifty percent by using SIO since GPS week 1 807.When using the different methods to eliminate the difference of coordinate reference frame, the accuracy of combined orbit dramatically changed, and the result using the rotation parameter of SINEX is better than that of using that of ERP. Finally, the combined orbit is calculated from 2014 July to 2015 July. Compared with IGS combined orbit, it is found that the three-dimensional difference is less than 3 mm, the mean RMS is 1.50 mm and the weighted mean RMS is 1.16 mm, according to the satellite accuracy code, proving the algorithm’s accuracy and stability.