Abstract: TDRSS and Double Satellite Positioning System(DSPS) usually consist of two or three GEO satellites and several LEO satellites.The satellite-to-satellite tracking data provided by these systems put forward the requiremens for multi-satellite joint orbit determination(OD).The difference between OD with known GEO ephemeredes and OD with unknown GEO ephemeredes was introduced.The measure model for the sum of range was established and the technica difficulties on multi-satellite joint OD were described.Finally,the OD accuracy was analyzed for the whole system.