In the complex highway traffic positioning environment such as slope, urban canyon and viaduct, there are massive and diverse positioning needs and complex positioning environment. The strength of BeiDou signal is weakened when it passes through the building space, and the building structure causes serious signal reflection and diffraction, which makes it difficult for BeiDou satellite signal to reach and use effectively, resulting in the decline of BeiDou system availability and the inability to provide reliable positioning services. Combined with the characteristics of high-density deployment of 5th generation mobile networks (5G) system, this paper proposes a BeiDou+5G hybrid positioning model and error correction method based on least squares residual Helmert posterior weighting. In the complex highway traffic environment, it can solve the problem of small number of visible satellites, optimize the geometric configuration of satellites, improve the positioning accuracy, and provide high-precision, all-weather, continuous, and real-time positioning for user terminals. Experiments show that the BeiDou+5G hybrid positioning model can greatly improve the positioning performance in complex highway traffic environment.