The　impact　factors　for　vehicle　load　were　ever　characterized　by　varied　parameters　among　different　countries,　and　it　is　now　commonly　described　by　the　fundamental　frequency　of　the　first　bending　mode　for　straightened　bridges,　but　there　are　still　no　computation　formulae　proposed　for　concrete　curved　bridges.　Massive　vehicle-bridge　interaction　analysises　are　carried　out　on　concrete　curved　box　girder　bridges　with　different　span　length,　curvature　radius,　section　type,　span　number　and　boundary　conditon,　using　a　validated　numerical　method.　Based　on　the　obtained　results,　the　impact　factors　for　varied　effects　are　discussed,　as　well　as　their　correlation　with　parameters　of　central　radius,　ratio　of　bending　to　torsional　rigidity,　integral　impact　coefficient　and　the　fundamental　frequency　of　vertical　bending　mode.　It　is　indicated　that,　the　impact　factor　of　interal　forces,　deflection　and　reaction　force　are　minus　correlated　with　the　discussed　parameters　except　for　ratio　of　bending　rigidity　to　torsional　rigidity.　The　impact　factors　are　most　closely　correlated　with　the　fundamental　frequency　of　vertical　bending　mode,　so　it　is　best　suited　to　characterize　the　change　of　impact　factors.　©　(2011)　Trans　Tech　Publications,　Switzerland.