Abstract: The quality of observation data will directly affect the global application process of satellite navigation system. In this paper, the quality of BDS／Galileo observation data has been analyzed and evaluated especially,observation data of 21 MGEX stations around the world from DOY66 to DOY76 of 2019 were used to assess data quality of BDS／Galileo system in terms of data availability, data completeness, multipath effect and so on. At the same time, data quality of BDS／Galileo system was compared with that of GPS. The results show that BDS／Galileo systems have the ability to provide global positioning service for user. The data quality of BDS is comparable to that of GPS and the data quality of Galileo system is slightly better than that of BDS／GPS.