Abstract: The position of LEO/MEO satellites used in the Mobile Satellite Systems vs the earth and the relative position of satellites are both time-variant.To establish InterSatellite Links (ISLs),it is necessary to make sure of the exact relative position of the satellites to calculate the azimuth and the distance of two satellites using ISLs.After presenting several constellation types and designing methods,the geometrical parameters of the ISLs are given, and the relationship between the azimuth and distance of two sate- llites in ISLs and constellation design in detail are analyzed.Some useful conclusions are also drawn.