The　broadband　sampling　oscilloscope　is　the　most　important　instrument　for　time-domain　measurements　of　signals.　However,　as　the　demand　for　precise　signal　measurements　increases,　the　jitter　of　broadband　sampling　oscilloscopes　is　becoming　a　growing　concern.　Jitter　not　only　reduces　the　clarity　of　the　signal　but　also　cause　waveform　distortion,　thereby　affecting　the　assessment　of　signal　quality　and　system　performance.　In　this　paper,　the　jitter　under　the　eye　diagram　measurements　of　sampling　oscilloscope　was　investigated.　Firstly,　the　eye　diagram　and　the　characterisation　of　jitter　in　eye　diagram　were　studied,　including　the　construction　of　the　eye　diagram　based　on　the　equivalent-time　sampling　technique,　the　impact　of　sampling　oscilloscope＇s　jitter　on　the　eye　diagram,　and　the　calculation　methods　of　jitter　under　eye　diagram　measurements.　Then,　the　impact　of　sampling　clock　jitter,　noise,　as　well　as　measurement　conditions　on　jitter　measurements　were　investigated.,　where　measurement　conditions　include　setting　sensitivity　on　oscilloscope,　the　amplitude　and　frequency　of　the　measured　signal,　the　number　of　sampling　points,　and　the　orders　of　the　code　types.　Finally,　the　influences　on　the　measurement　of　jitter　were　verified　by　constructing　the　actual　measurement　system.　©　The　Institution　of　Engineering　&　Technology　2024.