Abstract: In view of the impact of QZSS on the relative positioning performance of BDS-2 and BDS-3 short baselines,this paper analyzes the short baselines of different combinations of QZSS,BDS-2 and BDS-3 based on the 5km and 10km short baselines composed of IGS tracking stations relative positioning accuracy.It is found that QZSS can effectively improve the BDS-2 and BDS-3 satellite visibility and satellite space geometry,while the satellite visibility and satellite space geometry of BDS-2／BDS-3 combination is superior to any single system.In terms of positioning accuracy,the combined positioning accuracy of BDS-3 and QDSS is equivalent to BDS-2 in the case of missing data.At the same time.QZSS can effectively improve the relative positioning accuracy of BDS-2 and BDS-2／BDS-3.while BDS-3 shows better performance than QZSS in improvement of positioning accuracy of BDS-2.