Based on the 10 kilometers short baseline measurement data collected by International GNSS Service (IGS), therelative positioning accuracy of BDS dual-frequency, GPS dual-frequency and BDS/GPS combined dual-frequency is analyzed. Theresults show that the positioning accuracy of the three combinations can reach the centimeter level, the relative positioning accuracyof BDS is better than of GPS, and the BDS/GPS combined system has the highest accuracy. Compared with the single system, it issignificantly improved in the E,N and U directions, of which the E direction is increased by 16%, the N direction is increased by 18%,and the U direction is increased by 17%.