Making　full　use　of　wide-area　measurement　information　to　perform　static　quantitative　assessment　of　large　power　grids　is　critical　for　intelligent　monitoring　of　power　grids.　In　this　paper,　based　on　the　generalized　＇source-grid-load＇　equivalent　model,　a　method　for　constructing　the　static　stability　margin　index　of　large　power　grid　is　proposed.　First,　based　on　the　generalized　＇source-grid-load＇　equivalent　model,　the　power　generation　node　and　the　load　node　of　power　grid　are　respectively　equivalent　to　the　＇source＇　point　and　the　＇load＇　point.　Then　the　equivalent　＇　source-grid-load　＇　branch-related　electrical　parameters　are　obtained　through　computation　and　derivation,　and　the　entire　＇source-grid-load＇　system　is　given.　Then　based　parameters　of　the　above　equivalent　system,　the　static　voltage　stability　margin　and　the　power　angle　stability　margin　index　were　deduced,　and　the　static　stability　margin　index　of　the　large　power　grid　was　established,　and　the　rapid　quantitative　assessment　of　the　static　stability　of　the　large　power　grid　was　realized.　The　power　flow　simulation　results　of　the　IEEE　39-bus　system　verify　the　correctness　and　rationality　of　the　proposed　method.　Compared　with　the　traditional　method　(potential　energy　integration　method),　the　validity　of　the　proposed　method　is　also　verified.　©　2019　IEEE.