Voltage　sag　is　the　most　serious　power　quality　problem　in　the　three-phase　symmetrical　power　system.　The　influence　of　multiple　factors　on　the　voltage　sag　level　and　low　computational　efficiency　also　pose　challenges　to　the　prediction　of　residual　voltage　amplitude　of　voltage　sag.　This　paper　proposes　a　voltage　sag　amplitude　prediction　method　based　on　data　fusion.　First,　the　multidimensional　factors　that　influence　voltage　sag　residual　voltage　are　analyzed.　Second,　these　factors　are　used　as　input,　and　a　model　for　predicting　voltage　sag　residual　voltage　based　on　data　fusion　is　constructed.　Last,　the　model　is　trained　and　debugged　to　enable　it　to　predict　the　voltage　sag　residual　voltage.　The　accuracy　and　feasibility　of　the　method　are　verified　by　using　the　actual　power　grid　data　from　East　China.　©　2022　by　the　authors.　Licensee　MDPI,　Basel,　Switzerland.