Most　bridge　engineering　projects　can　be　accomplished　by　more　than　one　feasible　design　alternative.　We　must　perform　an　analysis　to　determine　which　one　of　the　mutually　exclusive　alternatives　is　preferred.　Economic　analysis　of　bridge　life-cycle　cost　is　one　of　factors　that　decide　feasible　design　alternatives　that　can　be　compared.　Based　on　computing-theory　of　highway　construction　cost,　we　analyzed　bridge　life-cycle　cost.　It　was　composed　by　bridge　constructing　costs,　operating　costs　which　occupy　a　biggish　proportion　of　bridge　life-cycle　cost　and　disposal　costs　which　pay　for　the　society,　environment,　bridge　configuration　research　and　implementation.　Bridge　constructing　costs　involves　planning,　project　feasibility　study,　designing　and　constructing　cost,　which　has　decreasing　influence　on　the　future　bridge　operating　period　costs.　Bridge　life-cycle　economic　cost　model　includes　a　bridge　configuration　design　cost　model,　constructing　a　cost　model,　management,　maintenance　and　a　repair　cost　model,　as　well　as　other　cost　models　like　projects　bring　benefits　to　user,　society　and　environment.　©　2011　ASCE.