Abstract: Based on the theory and method of GPS precise point positioning, this paper introduced a PPP observation model with multiple system combinations. This paper used observations from GPS, GLONASS, Galileo and BDS to study and analyze the positioning performance of 4-system combined PPP. The result showed that the accuracy of multi-GNSS PPP is much higher than single system PPP, GPS+GLONASS+GALILEO+BDS combination dynamic PPP in the three directions of the average deviation is about 0.7cm, 0.6cm and 1.7cm, the convergence time is about 15 ～ 20min. When the cutoff elevation angle increased, there was still a sufficient number of satellites. When the cutoff angle reached 30 degrees, still can reach cm-level positioning accuracy. The result of PPP solution on the airborne dynamic data showed that the result of the foursystem combination solves best with the result of GrafMov, and outperforms of two-system and single-system PPP.