In　order　to　study　the　fatigue　behavior　of　steel-concrete　composite　beams,　ANSYS　software　packet　was　employed　to　simulate　the　behavior　of　steel-concrete　composite　beams　under　fatigue　loads　in　this　paper.　After　the　finite　element　models　were　built　for　seven　composite　beams,　which　had　different　reinforcement　ratio　and　concrete　compressive　strength,　the　stress　amplitude　and　fatigue　life　were　analyzed,　then　the　relevant　S-N　curves　were　obtained,　and　a　comparison　was　made　among　the　experimental　results,　finite　element　analysis　and　related　design　codes.　The　results　show　that　when　the　cubic　strength　increases　from　36.4　MPa　to　41.8　MP,　the　fatigue　life　increases　1.48　times.　Under　the　same　conditions,　the　value　of　the　stress　amplitude　increases　9.9　MPa,　and　the　fatigue　lives　increase　128　thousand　and　240　thousand　cycles　in　terms　of　experimental　results　and　analytical　values　respectively.　The　reinforcement　ratio,　concrete　compressive　strength　and　stress　amplitude　are　the　main　influencing　factors　of　the　fatigue　life　for　composite　beams,　and　the　reinforcement　ratio　has　more　apparent　influence　on　the　fatigue　life　than　concrete　compressive　strength.