In　order　to　systematically　analyze　the　benefits　of　transit　metropolis　construction,　the　system　dynamics　(SD)　theory　was　used　to　construct　the　transit　metropolis　SD　simulation　model　from　the　four　subsystems　of　economy,　society,　environment,　and　transportation　supply　and　demand.　The　validity　of　the　SD　model　was　verified　by　the　social　and　economic　data　of　Nanchang　City　and　the　operational　data　of　the　bus　company,　and　the　quantitative　simulation　analysis　was　carried　out　by　taking　the　construction　of　the　transit　metropolis　in　Nanchang　as　an　example.　The　simulation　results　show　that,　in　2020,　the　number　of　motor　vehicles　in　Nanchang　will　reach　1.13　million　and　the　urban　population　will　reach　5.71　million.　It　is　necessary　to　build　a　transit　metropolis　for　the　sustainable　development　of　urban　transportation.　In　order　to　complete　the　transit　metropolis　creation　goal　of　60%　of　the　public　transit　mobility　sharing　rate,　the　proportion　of　public　transport　investment　in　the　total　transportation　investment　needs　to　be　adjusted　from　0.25　to　0.35.　As　a　result,　Nanchang　City　will　improve　after　the　peak　traffic　congestion　in　2022,　indicating　that　the　construction　of　the　transit　metropolis　will　have　a　positive　effect　on　Nanchang.　By　developing　new　energy　vehicles　and　low-emission　vehicles,　vehicle　emissions　will　drop　from　0.05　tons/year　to　0.04　tons/year,　and　overall　nitrogen　oxide　emissions　will　fall　by　70%,　which　is　significant　for　urban　environments.　The　research　results　provide　theoretical　support　for　the　significance　of　transit　metropolis　construction,　and　promote　the　sustainable　development　of　urban　transportation.