In　order　to　further　improve　the　dynamic　prediction　effect　of　bridge　engineering　life　cycle　cost,　a　life　cycle　cost　prediction　model　of　bridge　engineering　is　established　by　using　decision　tree　algorithm,　and　the　influence　coefficient　of　bridge　engineering　characteristics　on　cost　is　analyzed　by　data　acquisition　method.　After　analysis,　the　project　characteristics　which　have　great　influence　on　the　cost　of　bridge　engineering　are　determined.　The　decision　tree　algorithm　is　used　to　establish　the　dynamic　prediction　model　of　bridge　engineering　life　cycle　cost;　through　MATLAB　software,　a　good　bridge　cost　prediction　model　is　gradually　established,　and　the　model　is　trained,　modified　and　verified　according　to　the　actual　engineering　data.　The　dynamic　prediction　model　of　life　cycle　cost　investment　of　bridge　engineering　is　established　by　using　decision　tree　algorithm,　which　effectively　improves　the　prediction　accuracy　and　has　strong　practicability.　©　Published　under　licence　by　IOP　Publishing　Ltd.