The viscosities of the quinary system NaCl + KCl + CaCl2 + MgCl2 + H2O and its binary subsystems are measured in the temperature range of 288.15K-308.15K. The viscosity of binary solutions of MgCl2, NaCl, and CaCl2 increases with the increase in concentration. In contrast, for the binary solution of KCl, the viscosity decreases with increasing concentration at low temperature and low concentration. The extended Jones-Dole model that incorporates higher-order term parameters is used to fit the viscosity of binary solutions, with a maximum Average Absolute Deviation (AAD) of 1.42%. By comparing the values of the Pearson correlation coefficients, it is found that MgCl2 has the most significant impact on the viscosity of the quinary system MgCl2 + KCl + NaCl + CaCl2 + H2O, while the impact of KCl is the least. The modified extended Jones-Dole model, with the introduction of parameter Gi, can accurately predict the quinary system, resulting in a maximum AAD value of 0.63%. Moreover, the Hu model is also applied to predict the viscosity of the quinary system, achieving a maximum AAD value being 1.54%. Compared to the Hu model, the modified extended Jones-Dole model performs better. The viscosity calculation models for the quinary system MgCl2 + KCl + NaCl + CaCl2 + H2O in this study contribute key parameters for the design and optimization of the potassium chloride production process.