In　the　process　of　molten　salt　electrolysis　of　spent　tungsten　carbide　for　the　separation　of　tungsten　and　cobalt,　the　nature　of　the　molten　salt　has　a　crucial　impact　on　product　quality　and　efficiency.　In　this　study,　the　microscopic　and　macroscopic　models　of　the　diffusion　layer　of　Na2WO4–WO3–CoO　molten　salt　were　developed.　The　structure,　transport　properties　and　electroanalytical　behavior　of　Na2WO4–WO3–CoO　molten　salt　were　investigated　by　combining　molecular　dynamics　and　finite　element　simulation　under　different　CoO　and　WO3　molar　ratios　and　different　applied　electric　field　conditions.　The　cost　of　this　approach　is　relatively　low　compared　to　experiments.　It　was　found　that　the　addition　of　CoO　hinders　the　mass　transfer　and　increases　the　electrochemical　impedance.　The　reason　for　this　is　that　the　addition　of　CoO　leads　to　an　increase　in　the　entropy　of　the　molten　salt.　The　change　in　external　electric　field　does　not　affect　this　law.　The　calculated　results　are　in　general　agreement　with　the　available　experimental　data.　In　the　study　of　the　structure　of　molten　salts,　the　vacancy　volume　factor,　which　is　a　metric　for　evaluating　the　size　of　the　vacancy　volume　of　molten　salts,　was　proposed　for　the　first　time.　The　addition　of　CoO　also　affects　the　microstructure,　which　can　be　used　to　infer　changes　in　the　electrodeposition　products.　Experimental　results　of　electrodeposition　support　this　speculation.　This　study　confirms　that　a　combination　of　macroscopic　and　microscopic,　molecular　dynamics　and　finite　element　simulations　can　theoretically　aid　the　development　of　molten　salt　electrolysis　processes.　©　2023　Elsevier　B.V.