In　this　study,　Al　and　Zn　interlayers　are　added　separately　between　AZ31　and　ZK61　workpieces　to　investigate　the　method　of　eliminating　liquation　cracking　in　dissimilar　magnesium　alloy　resistance　spot　welding　(RSW).　Calculation　of　phase　diagram　technique　was　used　to　analyze　the　effect　of　Al　or　Zn　element　addition　on　the　metallurgical　reactions　in　the　nugget.　The　T-fS　curves　reveal　that　the　(fS)nugget　is　higher　than　(fS)ZK61　during　the　cooling　stage　of　the　AZ31/ZK61　RSW,　which　triggers　the　liquation　cracking.　Adding　Al　or　Zn　elements　into　the　nugget　can　change　the　T-fS　curve　of　the　fusion　zone,　thereby　restraining　the　liquation　cracking　at　different　degrees.　Microstructural　analysis　at　the　nugget/ZK61　interface　shows　that　the　cracks　become　discontinuous　in　the　AZ31/　Al/ZK61　samples,　while　the　cracks　are　eliminated　in　AZ31/Zn/ZK61　samples.　With　the　addition　of　interlayers,　the　microstructure　of　the　nugget　consisted　of　fully　equi-axed　dendrites,　while　the　microstructure　of　the　nugget　without　interlayer　consisted　of　a　mixture　of　columnar　and　equi-axed　dendrites.　Lap-shear　test　of　the　dissimilar　magnesium　alloy　RSW　joints　shows　that　the　mechanical　properties　of　the　samples　can　be　improved　significantly　when　the　liquation　cracking　is　restrained.　The　AZ31/ZK61,　AZ31/Al/ZK61,　and　AZ31/Zn/ZK61　samples　exhibit　nugget-drop-off,　partial-interfacial-partial-nugget-drop-off,　and　fully-interfacial　failure　modes,　respectively.