The　supersonic　condensation　process　of　methane-vapor-nonane　mixture　was　investigated　in　a　supersonic　nozzle.　First,　the　physical　model　of　the　ternary　mixture　of　the　supersonic　condensation　process　in　a　nozzle　was　established.　Second,　the　mathematical　model　of　the　ternary　mixture　of　the　supersonic　condensation　process　in　a　nozzle　was　determined　based　on　the　simulation　results　from　a　binary　mixture　supersonic　condensation　process.　This　work　developed　the　flow　characteristics　and　condensation　mechanism　of　the　ternary　mixture　in　supersonic　flows.　The　results　indicate　that　When　spontaneous　condensation　occurs,　the　release　of　latent　heat　causes　the　pressure,　temperature　and　the　Mach　number　to　change　abruptly.　Condensation　is　still　an　expansion　process,　and　after　the　condensation　shock,　water　vapor　began　to　condense　spontaneously　at　x　=　4.0　mm.　The　water　vapor　droplets　served　as　the　external　nuclei　of　the　nonane,　which　decreased　the　energy　barrier　of　the　nonane　vapor,　allowing　it　to　condense　at　a　lower　super-cooling　(383　K)　and　super-saturation　temperature　(37.4　K).　It　was　observed　that　the　existence　of　water　vapor　accelerated　the　condensation　of　the　nonane　vapor.　(C)　2016　Elsevier　B.V.　All　rights　reserved.