Abstract: The construction of BDS-3 has been completed. At this time, it is very meaningful and necessary to carry out the study and analysis of BDS-3 data quality and positioning performance. Observation data of MGEX stations were used to assess the observation data quality and pseudorange single-point positioning accuracy of BDS-3. Meanwhile, the positioning accuracy of BDS-2 and GPS were compared with BDS-3. The results show that the data integrity rate of BDS-3 at each station is above 95%. The average signal-to-noise ratio of each frequency band is higher than 45 dB·Hz, but signal-to-noise ratio of GEO satellite fluctuates frequently. The average value multipath error of various types of BDS-3 satellites are all less than 35 cm, and the pseudorange noise of most BDS-3 satellites is generally less than 0.3 m. Compared with BDS-2 and BDS-3, the positioning accuracy of BDS-2/BDS-3 has been improved to different extents, but the improvement of BDS-3 positioning accuracy in high latitude areas is very small. BDS-3 can obtain a positioning accuracy better than 3 m and 4 m in horizontal and vertical directions in all regions of the world, which is roughly comparable to GPS positioning performance.