Phase　diagrams,　also　known　as　equilibrium　phase　diagrams,　serve　as　a　road　map　for　materials　design.　However,　preparation　process　of　coatings　(such　as　Physical　Vapor　Deposition,　PVD)　is　generally　far　from　equilibrium　and　results　in　metastable　phases.　Thus,　the　CALPHAD　(Calculation　of　Phase　Diagrams)　approach　faces　a　challenge　in　calculating　the　metastable　phase　diagrams　for　PVD　coating　materials.　Here　we　summarized　the　development　of　the　modeling　methodology　for　the　metastable　phase　diagrams,　where　the　model　with　critical　surface　diffusion　distance　established　in　recent　years　were　highlighted.　The　CALPHAD　approach,　first-principles　calculations　coupled　with　high-throughput　magnetron　sputtering　experiments　were　used　to　model　the　atomic　surface　diffusion,　while　only　one　key　combinatorial　experiment　was　performed　to　obtain　the　basic　data　for　the　computation,　and　the　calculated　metastable　phase　diagrams　were　confirmed　by　further　experiments.　Therefore,　the　database　of　the　stable　and　metastable　phase　diagrams　can　be　established,　which　will　be　used　to　guide　the　design　of　the　ceramic　coating　materials　by　the　relationship　of　composition,　processing,　microstructure,　and　performance.　This　model　can　also　help　to　achieve　the　goal　to　shorten　the　time　and　reduce　the　costs　of　materials　research　and　development.　©　2020,　Science　Press.　All　right　reserved.