The　optical　pulse　standard　method　is　based　on　the　traditional　pulse　standard　method.　This　method　is　that　converting　the　optical　pulse　into　electrical　pulse　through　the　detector　and　then　calibrating　the　broadband　sampling　oscilloscope.　In　the　paper,　according　to　the　optical　pulse　standard　method,　a　method　of　evaluating　the　uncertainty　of　calibrated　bandwidth　of　oscilloscope　is　proposed.　Firstly,　the　influencing　factors　of　measurement　uncertainty　are　analyzed　and　the　calculation　formula　of　standard　uncertainty　is　derivated;　Then　the　transfer　algorithm　of　uncertainty　is　studied;　Finally,　the　composite　uncertainty　of　calibrated　bandwidth　is　evaluated.　The　results　show　that　the　method　is　scientific　and　reasonable.