Abstract: In areas where GNSS signals are easily sheltered, the number of visible satellites in a single navigation system is small, and the positioning performance is not ideal or even difficult to meet the requrements of positioning needs. In this paper, the improvement of BDS-3's positioning performance in shadow environments is analyzed in different area. Based on the observation data of MGEX monitoring stations in different regions of the world, three modes of GPS, BDS-3, and BDS-3/GPS combined positioning are used to perform pseudo-range single-point positioning under different simulated shadow environments, and the number of visible satellites in each mode is analyzed, together with epoch utilization, GDOP value and positioning accuracy. The results show that in the northern hemisphere, compared to shadow in other direction, the GPS mode has the highest positioning stability and accuracy in the south of low latitudes, and the highest positioning stability and accuracy in the north of the middle and high latitudes. BDS-3 and BDS-3/GPS mode has the same positioning accuracy in all directions in low latitude areas. In mid-latitude and mid-high latitude areas, the accuracy of north shadowed is significantly better when shadow is in the north direction than that of other directions. The BDS-3/GPS combined positioning mode greatly increases the number of available satellites, improves the epoch utilization rate, improves the satellite spatial geometry, and reduces the GDOP value, which is significantly better than a single system in stability and positioning accuracy.