Abstract: With the success of the global networking of the BeiDou Navigation Satellite System (BDS), the application research based on the BDS is in full swing, especially the multi-frequency and multi-mode fusion positioning including BDS is becoming the focus of research. This article uses BDS (BDS-3), GPS, GLONASS, and Galileo observation data from multiple stations in the MGEX (Multi-GNSS Experiment), based on RTKLIB open source code, and performs the precision point positioning experiment of the three combined systems BDS/GPS, BDS/GLONASS, and BDS/Galileo on the Visual Studio 2017 platform. The positioning performance of the three combined systems is compared and analyzed from static PPP, dynamic PPP, number of visible satellites, and attenuation of precision (DOP). The experimental results show that the BDS/GPS combined system has the largest number of visible satellites and the smallest DOP value. The accuracy of the three directions after static PPP convergence is better than 6 cm. Whether it is static or dynamic, its positioning performance is the best. The dynamic precise point positioning (PPP) positioning jitter of the BDS/GLONASS and BDS/Galileo combined system is relatively large. It can be seen that the number of satellites is smaller than the BDS/GPS combined system, and the convergence time is longer. The dynamic PPP positioning performance of the two is also worse than that of the BDS/GPS combined system.