Based　on　the　on-line　monitoring　system　of　aluminium　alloy　spot　welding　the　database　was　constructed.　The　database　connected　with　the　on-line　monitoring　system　based　on　LabVIEW　to　record　and　slave　the　real-time　quality　information　of　nuggets.　The　database　also　supports　nugget　information　querying　and　managing　and　worker　information　querying　and　managing.　This　functions　are　very　suitable　for　aerial　manufacture　and　the　factory　practicality.　The　X-chart　is　used　to　estimate　the　critical　value　of　the　nugget　quality　by　analyzing　the　database　information,　and　the　critical　value　is　feed　back　to　the　on-line　monitoring　system.　The　results　of　experiments　indicate　that　this　on-line　monitoring　system　has　achieved　high　precision　in　the　nugget　quality　estimation,　and　it　has　been　used　in　the　aerial　products　spot　welding　now.