The　nose-to-nose　calibration　procedure　can　obtain　the　impulse　response　and　complex　transfer　function　more　accurately,　comparing　with　other　technologies　to　calibrate　broadband　sampling　oscilloscope.　Because　it　should　meet　the　needs　to　connect　the　two　oscilloscope　input　channels　directly　in　nose-to-nose　calibration　procedure,　it　is　very　difficult　to　operate　the　oscilloscopes　through　front　panel.　So　an　auto-calibrating　system　of　broadband　sampling　oscilloscope　based　on　nose-to-nose　calibration　procedure　is　introduced.　The　system　build-up,　system　function　and　calibration　results　are　described　in　detail.　The　calibration　of　this　system　is　implemented　on　PC.