In　order　to　research　the　impact　effect　characteristic　of　a　long-span　irregular　CFST　arch　bridge,　the　dynamic　response　analysis　on　the　interaction　of　vehicle　and　bridge　was　carried　out　by　the　self-compiling　computing　program　for　the　Yitong　River　bridge　under　construction　in　Changchun　city.　The　influence　of　road　surface　roughness,　vehicle　speed　and　damping　on　impact　effect　of　bridge　was　analyzed　by　theory.　Results　show　that　the　effect　of　road　surface　roughness　on　vibration　response　of　the　irregular　arc　bridge　is　significant,　keeping　good　roughness　level　will　decrease　impact　factors.　The　influence　of　vehicle　speed　on　impact　effect　is　related　with　the　primary　modes　of　response,　and　hence　increasing　vehicle　speed　may　not　increase　impact　factors.　Damping　ratio　of　the　structure　does　not　affect　impact　factors　significantly　when　it　is　changed　in　a　given　scope　by　specification,　and　damping　ratio　of　5%　can　be　used　in　the　design　for　security.　Moreover,　reference　values　of　impact　factors　of　the　bridge　are　given　in　the　study.