Resistance　spot　welding　quality　real-time　monitoring　of　aluminum　alloy　is　realized　by　distributed　multiple-sensor　synchronous　collection　system　and　the　related　data　processing　software　is　also　developed　by　using　LABVIEW　graphical　language.　The　results　show　that　the　endo-expulsion　in　spot　welding　is　related　to　the　notching　curve　of　voltage　and　electrode　displacement　signal.　Moreover,　there　is　a　correlation　between　the　high　frequency　impulse　amplitude　and　duration　of　the　electrode　pressure　signal　and　the　expulsion　strength　index,　and　three　characteristics　simultaneously　or　separately　occur　according　to　the　expulsion　strength　index　in　spot　welding.　Resistance　spot　welding　quality　can　be　reflected　by　nine　characteristics　of　high　signal-to-noise　ratio,　and　they　become　the　base　of　on-line　quality　classification　of　aluminum　alloy　spot　welding　in　future.　Furthermore,　using　principal　component　analysis　may　implement　the　information　fusion　and　data　compression.　The　percentage　of　spot　welding　quality　classification　accuracy　can　reach　98%.