In　order　to　provide　technical　foundation　for　using　widely　synthetic　macro-fiber　in　earthquake　region,　this　paper　studies　on　the　seismic　performance　of　synthetic　macro-fiber　reinforced　concrete　beam　under　low　reversed　cyclic　loads　by　the　experimental　method,　and　emphasizes　on　discussing　the　failure　pattern,　characteristic　loads　and　deflections,　ductile,　stiffness　degradation　and　energy　dissipation　capacity,　ductile　evaluating　method　of　synthetic　macro-fiber　reinforced　concrete　beam　is　analyzed,　the　ductile　index　of　synthetic　macro-fiber　reinforced　concrete　beam　is　larger　49%　than　that　of　plain　concrete　beam,　and　presents　good　seismic　performance.