Considering the construction demand of Beidou global navigation satellite system (BDS) in China, it is necessary to analyze the positioning performance of Beidou regional service satellite system (BD2), BDS and their combination with GPS, GLONASS and Galileo system.To BD2，the positioning performance of BD2, GPS/BD2 and GPS/BD2/GLONASS is analyzed by using two methods, simulation and factual observation data.Results show that BD2 completely meet the requirements of positioning performance in Beidou public service performance specification, and with the increase of the number of constellations，the positioning accuracy gradually improves, and the improvement of positioning performance in high-latitude regions is obvious when GLONASS is joined. To BDS, an analysis is made mainly by the method of simulation. The simulation results show that the positioning performance of the Asian-Pacific region still shows obvious improvement, and the mean value of PDOP in other regions reaches 1.2 to 1.6.In addition, the combination of the four major navigation systems will make obvious improvement on the positioning performance for polar regions.