BeiDou navigation satellite system (BDS) has been officially built and opened in July 2020. BDS-3 adds new signals B1C and B2a on the basis of old signals B1I and B3I. In order to comprehensively evaluate the positioning performance of new signals B1C and B2a of BDS-3, the positioning performance of GPS (Global Positioning System), BDS-3, BDS-2/BDS-3 old and new signals and the positioning performance of BDS combined with GPS at different frequency points are tested. The positioning performance of BDS (B1I+B3I, B1C/B2a) + GPS (L1+L2) combined static PPP (Precise Point Positioning) is analyzed and compared with that of single satellite system. The experimental results show the positioning accuracy of BDS-3 (B1C/B2a) in E (East), N (North), U (Up) direction is better than 1.25cm, 0.89cm, 1.67cm, respectively. The positioning accuracy of BDS-3 new and old frequency points in E and N directions is the same as that of GPS L1/L2, and the positioning accuracy of new frequency points in U direction is higher than that of GPS L1/L2 and BDS-3 old frequency points, which is 34.2% higher than that of old frequency points. The convergence time of the new frequency point is 25.9min, which is 12.7% higher than that of the old frequency point. Compared with BDS and GPS single systems, BDS/GPS positioning accuracy and convergence time of the combined system have been significantly improved. BDS-3 (B1C/B2a)+GPS has the same positioning accuracy as BDS-3 (B1I/B3I)+GPS in E and N directions. In the U direction, the positioning accuracy of the former is significantly improved compared with the latter, which is increased by 17.2%. The convergence time of the new frequency point of the combined system is 20.1min, which is 17.6% higher than that of the old frequency point.