Abstract: Mobile communication service implemented by a constellationcomposed of small LEO satellites is a primary trend of development of satellitecommunication.Either of the uses of LEO and GEO satellite constellations formobile communication service has its own strong and weak points.This paperanalyses and compares the two satellite constellations in view of economics withemphasis on cost of space segments,i.e.the development cost of satellites andtheir launch cost,gives the specific calculation formula and results,and finallyconcludes that the lower the orbit height is,the higher the total cost is,andthe cost of GEO satellite constellation is the lowest.But not only its economicsbut also its effects on promoting technology must be considered in decisionmaking on whether or not the LEO communication satellite network need to bedeveloped.