The BDS-3 basic system has already been established, starting to provide global service. As a new generation navigation system, the BDS-3 adopts a global ionospheric model, called BDGIM. Single-frequency users can use the BDGIM along with nine ionospheric parameters broadcasted in the navigation message to perform ionospheric correction. This paper analyzes the deficiency of the current BDS and GPS Klobuchar models, and then by using the high precision CODE’s global ionospheric map (GIM) as a reference, the precision of BDGIM model is evaluated. Finally, the performance of applying this model to the positioning is verified by experimental data. The results show that the global accuracy of the BDGIM model is about 3.6 TECU, which is better than that of the Klobuchar model and more uniform on a global scale. In terms of the BDS standard point positioning, ionospheric correction with the BDGIM model obtains higher accuracy compared to that with the Klobuchar model, especially in the vertical direction.