为充分发挥BDS-3和Galileo多频信号的定位优势，对BDS-3和Galileo四频宽巷组合进行优选，并基于优选后的组合构建适用于BDS-3单系统、Galileo单系统、BDS-3/Galileo双系统和BDS-3/Galileo/GPS三系统的多频定位模型，通过对多频长基线数据进行测试，对比分析4种定位模式下的定位精度和稳定性。结果表明，在对长度超过500 km的长基线进行定位解算时，BDS-3单系统定位精度优于Galileo单系统；水平和垂直方向上BDS-3/Galileo双系统组合定位精度均可达到dm级，较BDS-3单系统提升幅度分别在10%和25%以上，稳定性也有明显改善；BDS-3/Galileo/GPS三系统定位精度较双系统也有提升，提升幅度在10%左右；双系统和三系统的相对定位精度均达到1×10^－9 m量级，可以满足长基线精密定位要求。卫星系统的增加不仅可增大可视卫星数，还可增强卫星的几何结构，从而有效提高定位精度和稳定性。

To take full advantage of BDS-3 and Galileo multi-frequency signals on positioning, we make a  proper selection of BDS-3 and Galileo four-frequency wide-lane combinations, and construct multi-frequency positioning models which are suitable for BDS-3 single-system, Galileo single-system, BDS-3/Galileo dual-system as well as BDS-3/Galileo/GPS triple-system, based on the proper combinations. We compare and analyze the multi-frequency long baseline data, positioning accuracy and stability of four positioning models. The results show that when the long-baseline is over 500 km, the positioning accuracy of the BDS-3 single-system is better than that of the Galileo single-system. The positioning accuracy of the BDS-3/Galileo dual-system can reach the decimeter level in both the horizontal and vertical directions, which is more than 10% and 25% higher than that of the BDS-3 single-system, and the stability is also significantly improved. Compared with the dual-system, the positioning accuracy of the BDS-3/Galileo/GPS triple-system is improved by about 10%. The relative positioning accuracy of the dual-system and the triple-system reaches 1×10^-9 m, which can meet long-baseline precise positioning requirements. The increase of satellite systems not only increases the number of visible satellites, but also enhances the geometry of the satellites, which improves the positioning accuracy and stability effectively.