An Extended Kalman Filtering algorithm of autonomous orbit determination is presented in this paper. This algorithm can determine the satellite position and velocity vectors using cross-link range information. The STK satellite software developed by the AGI Company is used to create the GPS constellation scene，and cross-link range is derived based on quasi-distance among GPS satellites．Peak value of error is decreased by using the value of Geometric Dilution Of Precision(GDOP) to replace reference satellite. The simulation results demonstrate that the precision of orbit determination is greatly improved.