Identification　of　time-varying　cable　force　is　an　important　content　of　structural　condition　evaluation　and　health　diagnosis　of　a　cable-stayed　bridge.　However,　this　problem　has　not　been　well　solved　so　far.　Based　on　an　improved　multisynchrosqueezing　transform　and　an　efficient　ridge　extraction　algorithm,　a　new　method　for　time-varying　cable　force　identification　of　stay　cables　was　proposed　in　this　paper.　Firstly,　the　time-frequency　spectrum　was　obtained　by　using　the　vibration　acceleration　response　of　the　cable,　and　then　the　time-frequency　ridge　in　the　time-frequency　spectrum　was　extracted　to　obtain　the　instantaneous　frequency　of　the　cable.　Finally,　the　time-varying　cable　force　was　calculated　according　to　the　tension　string　theory.　The　applicability　and　precision　of　the　method　were　verified　by　a　typical　numerical　case　of　cable-stayed　bridge　and　cable　tests.　Results　show　that:　in　the　numerical　case,　under　the　noise　level　of　10%,　the　average　error　of　time-varying　cable　force　identification　is　less　than　1.99%,　and　the　maximum　error　is　5.09%；　in　the　test,　the　average　error　of　time-varying　cable　force　identification　is　less　than　2.52%,　and　the　maximum　error　is　8.77%.　The　preliminary　verifying　results　prove　that　the　proposed　method　has　good　identification　accuracy　and　noise　robustness.　©　2023　Chinese　Vibration　Engineering　Society.　All　rights　reserved.