In　order　to　obtain　the　effect　of　vehicle　load　on　bridge　structure　in　the　state　of　lanes　merging,　vehicle　load　effect　analysis　method　for　expressway　bridge　was　studied　based　on　vehicle　load　data　collected　by　WIM　system　on　a　continuous　girder　bridge.　Firstly,　according　to　the　feature　of　lanes　merging　of　vehicles,　basic　distribution　characteristics　of　vehicle　load　including　vehicle　weight,　axle　load,　axle　spacing　and　vehicle　spacing　were　obtained　by　using　EM　calculation　method.　Secondly,　to　solve　two　cases　in　the　state　of　lanes　merging,　including　decrease　of　vehicle　spacing　and　vehicle　jam　the　corresponding　random　vehicle　load　flow　simulation　method　was　presented.　Finally,　bridge　load　effect　evaluation　value　in　the　state　of　lanes　merging　was　obtained　by　combining　stochastic　vehicle　influence　line　and　extreme　value　distribution　theory,　and　the　influence　of　vehicle　spacing　on　load　effect　was　studied.　The　results　show　that　the　total　vehicle　weight,　axle　weight　and　axle　spacing　obey　the　mixed　Gauss　distribution,　and　the　vehicle　spacing　obeys　the　logarithmic　normal　distribution.　The　present　method　can　be　well　applied　to　analysis　of　the　vehicle　load　effect　in　the　state　of　lanes　merging,　and　the　load　effect　are　about　1.13　and　1.03　times　of　the　exceeded　truck-20　and　the　highway　grade　I　respectively.　When　is　the　lanes　merging　and　vehicle　jam　happening　in　meantime,　the　corresponding　vehicle　load　effect　are　1.29　and　1.17　times　of　the　exceeded　truck-20　load　effect　and　the　highway　grade　I　respectively.　It　is　also　found　that　effect　of　vehicle　spacing　linearly　relates　to　the　distance　between　two　vehicles　when　vehicle　spacing　is　between　2-5　m,　and　the　actual　vehicle　load　effect　is　definitely　less　than　the　design　vehicle　load　effect　when　vehicle　spacing　is　controlled　at　more　than　10　m.　The　research　results　can　provide　references　for　the　evaluation　of　bridge　carrying　capacity　and　the　traffic　control　in　the　state　of　lanes　merging.　©　2017,　Editorial　Department　of　Journal　of　Chang＇an　University　(Natural　Science　Edition).　All　right　reserved.