In　order　to　solve　the　problems　of　low　efficiency　and　long　time　consuming　when　using　BPA　electromechanical　transient　program　to　simulate　large-scale　provincial　power　grid　voltage　sag,　this　paper　proposes　and　implements　a　parallel　fast　simulation　scheme　of　voltage　sag　based　on　multi-core　technology.　Firstly,　analyze　the　data　file　of　BPA　software　to　obtain　the　bus　and　line　information　of　the　whole　network;　secondly,　automatically　generate　a　large　number　of　fault　information　according　to　the　BPA　format　requirements　and　write　them　into　the　transient　stability　file　one　by　one;　thirdly,　call　the　BPA　simulation　program　in　parallel　through　multi-core　technology　and　store　the　data　of　sag　results;　finally,　through　the　simulation　of　the　whole　network　line　sag　of　a　province,　and　compare　with　the　current　situation　The　time-consuming　comparison　of　BPA　based　voltage　sag　simulation　schemes　shows　that　the　proposed　method　can　effectively　speed　up　the　simulation　speed,　save　time　and　cost,　and　provide　a　large　number　of　reference　data　for　voltage　sag　research　and　risk　prediction.　©　2022,　The　Author(s),　under　exclusive　license　to　Springer　Nature　Singapore　Pte　Ltd.