When　applying　a　dynamic　programming　algorithm　to　train　speed　trajectory　optimization,　there　is　a　problem　of　too　many　discrete　points　which　leading　to　dimension　disaster.　Different　from　using　uniform　discretization　of　the　time　and　space　by　previous　research,　In　this　paper,　a　train　operation　model　is　proposed　based　on　conditions　(speed　limit　and　slope　change)　and　described　in　the　network　diagram.　Armed　with　this　model,　through　the　pre-planning　of　the　line,　the　optimization　model　of　train　operation　is　established,　and　the　dynamic　programming　algorithm　is　utilized　to　find　the　global　optimal　value　of　train　traction　energy　consumption.　Taking　Beijing　Yizhuang　line　as　a　simulation　case,　the　validity　of　the　proposed　model　is　verified　by　comparing　common　optimization　algorithms.　The　results　demonstrate　that　the　proposed　model　can　effectively　reduce　the　calculation　time　of　the　dynamic　programming　algorithm　by　95.06%,　and　has　better　optimization　effect.　The　energy-saving　effect　reaches　6.0806%.　©　Published　under　licence　by　IOP　Publishing　Ltd.