Abstract：This paper introduces the principle of centralized real-time autonomous navigation(AutoNav) based on the parameter decomposition filter, and also presents the simulation method for inter-satellite cross-link observations. Based on the simulated observations for the simulated constellation of BDS, 60 days’ AutoNav is performed. The influence of observation noise and residual systematic errors to the precision of AutoNav is analyzed. The results indicate that observation noise has no distinct effect on the precision of AutoNav. However, the residual systematic error has a great influence and needs to be carefully corrected. Otherwise, there are no differences regarding the influence of the observation noise and residual systematic error on GEO, IGSO and MEO satellites.