When selecting a suitable molten salt electrolyte system for liquid metal batteries (LMBs), it is crucial to have an accurate understanding of the local structures and transport properties of molten salt mixtures. In this study, molecular dynamics simulations have been employed to calculate such properties of (Li, Na, K, Cs)Cl and (Li, K, Rb, Cs)Cl quaternary molten alkali chloride systems at 700-1000K using the Born-Mayer-Huggins potential. The results show that the density and shear viscosity of the molten salt electrolyte increase when the average cation radius increases, while the self-diffusion coefficient and ionic conductivity decrease. Increasing the temperature in LMBs can enhance the diffusibility and electroconductivity of the molten salt electrolyte and reduce the density and shear viscosity to a certain extent. Overall, the calculated results provide a useful reference for the selection of molten salt electrolytes with reasonable composition to optimize the electrochemical performance of LMBs.Graphical AbstractThe molten salt mixtures as the electrolytes have a crucial effect on the performances of LMBs. The transport properties such as ionic conductivity, shear viscosity and self-diffusion capacity of quaternary molten salt systems (Li, Na, K, Cs)Cl and (Li, K, Rb, Cs)Cl have been calculated by MD simulation, and the simulation results can provide guidance for the researches of LMBs in the future. [GRAPHICS]