The PROD (precise relative orbit determination) for the LEO (low earth orbit) formation-flying satellites based on BDS (BeiDou satellite navigation system) was studied. Due to the lack of experimental data, the simulation method was used. Results show that the average number of visible BDS satellites at altitude of 500 km is about 9.7. Because of the GEO (geostationary earth orbit) satellites and IGSO (inclined geosynchronous earth orbit) satellites, the LEO satellites can observe more BDS satellites over the Asia-Pacific region. When only the observation noise is considered, the accuracy of PROD based on BDS is 0.74 mm. Furthermore, the influence of ephemeris errors is analyzed. For a few kilometres separation of the LEO satellites, the effect of ephemeris errors on PROD could be ignored. However, for a 200 km separation of the LEO satellites, the SD (single difference) ephemeris errors of GEO satellites would be on the order of centimetres. The experimental results show that when IGSO satellites and MEO satellites co-work with GEO satellites, the accuracy decreased from 1.09 mm to 0.96 mm, decreased by 13.54%. Finally, the conclusion is that the accuracy of PROD based on BDS can reach sub-millimeter level after the remaining errors are processed, the differences of the PROD results are not apparent between different regions. When relative position between satellites is only a few kilometres, the GEO satellites and IGSO satellites can improve the accuracy of PROD all over the world. In the future, BDS will be widely used in PROD of LEO satellites.