Abstract: In this paper, three typical low earth out satellite constellations which are Iridium NEXT system abroad, "Hongyan" constellation and "CentiSpace" of China, were selected to analyze the navigation enhancement of Beidou navigation satellite system (BDS) from the aspects of signal free space transmission loss, number of visible satellites and dilution of precision. The results show that the enhancement ability of LEO constellations to navigation system are different due to different constellation structure and number of satellites. As polar orbit constellations, Iridium NEXT system and "Hongyan" constellation have strong navigation enhancement ability in polar regions, but with the decrease of latitude, the enhancement ability decreases obviously. While the "CentiSpace" with inclined orbit as the main part has stronger navigation enhancement ability in middle and low latitudes.