Abstract: Under complex ionospheric conditions, the accuracy of broadcast ionospheric models in global navigation satellite systems is affected to varying degrees. To address this common issue, this study performs a multidimensional refinement of the system-side parameter estimation and model representation of the BeiDou Global Ionospheric Delay Correction Model (BDGIM). The results indicate that, by updating the ionospheric background field on a semiannual basis, the mean root mean square error (RMSE) is reduced from 11.78 TECU to 7.84 TECU, representing an improvement of approximately 33%. After incorporating globally distributed overseas stations, the RMSE is further reduced from 9.92 TECU to 8.69 TECU, with the most pronounced improvement observed in low-latitude regions. By further introducing Tianmu low Earth orbit (LEO) radio occultation observations, the global mean error decreases from 15.16 TECU to 10.45 TECU. Moreover, a 9-parameter regional modified spherical harmonic model is developed, achieving an accuracy improvement of approximately 26.8%. In addition, for the negative values occasionally occurring in some high-latitude regions, the application of a minimum-value constraint is recommended. These results demonstrate that the proposed methods can significantly improve the accuracy, stability, and regional applicability of BDGIM.