For　urban　rail　transit　(URT)　operation　and　management,　it　is　important　to　accurately　estimate　the　spatial　and　temporal　passenger　flow　distribution　spreading　all　over　the　network.　Unfortunately,　a　literature　review　shows　that　the　existing　simulation-based　methods　and　dynamic　assignment　methods　are　not　able　to　satisfactorily　achieve　the　goal.　Therefore,　this　paper　proposes　a　train　operation　diagram-based　equilibrium　model　to　estimate　the　spatial　and　temporal　passenger　flow　distribution　in　a　URT　network.　First,　a　space-time　URT　network　is　constructed　based　on　the　train　operation　diagram,　and　then　an　equilibrium　passenger　flow　assignment　model　is　proposed　for　a　URT　system.　Factors　including　travel　time,　transfer　time,　in-train　congestion,　and　station　congestion　are　considered.　An　improved　shortest-path　algorithm　for　the　space-time　URT　network　is　presented,　in　which　the　transfer　constraints　are　fully　considered.　Finally,　the　proposed　model　and　algorithm　are　verified　and　analyzed　by　using　a　numerical　example　and　are　also　demonstrated　in　the　Beijing　URT　network.　The　proposed　model,　which　is　based　on　the　train　operation　diagram　and　with　the　consideration　of　transfer　constraints,　is　beneficial　to　estimating　passenger　flow　within　a　URT　network　and　to　managing　URT.　(c)　2020　American　Society　of　Civil　Engineers.