The solubilities of the system LiCl-Li2SO4-Li2B4O7-H2O at 298.15 K were calculated based on the Pitzer model and its HW extended model. The values of the parameters were derived from literature or through fitting with the solubility data of the respective ternary system in literature. By comparing the experimental values with the calculated solubilities, it is shown that the model can be used to successfully predict the solubilities of the system under investigation. The parameters and equilibrium constants obtained in this study can furthermore be used for solubility calculations of more complicated systems that contain Li2B4O7, and the results can provide a theoretical basis for the extraction of lithium borate from salt lake brine sources.