The　stability　of　fusion　welding　structures　of　light　alloy　joints　is　significant　to　the　aeronautic　and　astronautic　fields.　In　this　paper,　the　research　subject　is　investigated　from　the　perspective　of　grain　boundary　structures.　The　fusion　welding　zone　of　a　5　series　aluminium　alloy　was　taken　as　the　example,　and　the　scanning　electron　microscopy,　electron　backscatter　diffraction　(EBSD),　and　statistical　grain　boundary　structure　analysis　methods　were　utilized.　First,　the　heat-affected　zone　(HAZ),　equiaxed　zone　(EQZ),　and　fusion　zone　(FZ)　were　spatially　separated.　Then,　the　corresponding　misorientation　angles　across　the　grain　boundary　planes　were　calculated　for　each　zone.　Next,　the　orientation　texture　of　habit　planes　was　studied　via　five　parameter　analysis　(FPA)　method　for　the　separated　zones.　Based　on　these　work,　the　beneficial　correlations　between　the　orientation　texture　of　habit　planes　and　the　structural　stability　of　the　material　were　established.　With　the　combination　of　stereology　and　the　structure　of　light　alloys,　the　research　develops　the　extraction　and　classification　technology　of　grain　boundaries　in　the　spatial　sense,　and　proposes　the　misorientation　angle　analysis　method　of　grain　boundary　planes,　which　realizes　a　positive　feedback　of　grain　boundary　structures　to　material　properties,　and　can　provide　effective　references　for　similar　studies.　©　2022,　Editorial　Board　of　Material　Science　and　Technology.　All　right　reserved.