The precise point positioning (PPP) mode has been widely used in many fields, such as vehicle navigation, surveying and mapping, and earthquake monitoring etc. In recent years, multi-GNSS is an obvious trend with the increasing number of satellites. In this paper, BDS/GPS PPP is researched by comparing the calculation of the data from global Multi-GNSS Experiment (MGEX) with BDS and GPS PPP. The results show that the average RMS of BDS static PPP is 4.35 cm, 3.01 cm, 6.40 cm while the average RMS of GPS static PPP is 1.21 cm, 0.48 cm, 1.79 cm in east, north and up directions, respectively. The average RMS of BDS/GPS static PPP is 1.21 cm, 0.50 cm, 1.87 cm in east, north and up directions, respectively. In kinematic PPP, the accuracy of positioning in BDS is better than 10 cm and 15 cm in horizontal and vertical directions respectively. While the accuracy of GPS and BDS/GPS is all better than 5 cm and 8 cm in horizontal and vertical directions, respectively. The number of satellites in BDS/GPS is the double of that in single system. And the spatial structure of combined system is greatly enhanced which can improve the stability of positioning. In addition, whether in static PPP or kinematic PPP, the combined system can greatly shorten the convergence time and reduce jitter compared with single system especially with BDS PPP.