This　work　presents　the　analytical　acoustic　model　to　investigate　the　interaction　mechanism　between　the　state　of　charge　(SOC)　of　lithium-ion　battery　and　the　propagation　characteristics　of　ultrasonic　guided　waves.　Meanwhile,　the　multi-layered　porous　structure　characteristics　of　lithium-ion　batteries　are　focused　on,　the　Biot　theory　and　transfer　matrix　method　are　introduced　to　construct　the　analytical　acoustic　theory　model　of　lithium-ion　batteries.　The　mechanical　performance　(modulus　and　density)　of　the　electrode　is　dynamically　changing　during　cycling,　which　will　influence　the　dispersion　characteristics　of　ultrasonic　guided　waves　in　lithium-ion　battery.　Based　on　this,　the　intrinsic　connection　between　the　SOC　and　the　guided　wave　dispersion　curve　of　lithium-ion　battery　is　numerically　analyzed.　Moreover,　the　frequency　domain　simulation　model　with　equal　structural　characteristics　is　established　to　verify　the　validity　of　the　above　theoretical　results.　Theoretical　results　performed　on　the　customized　pouch　cell　show　that　the　changes　in　time　of　flight　resulting　from　shifts　in　the　group　velocity　of　guided　wave　A0　mode　correlate　strongly　with　the　SOC.　An　ultrasonic　guided　wave　detection　experiment　system　is　built　to　extract　the　variations　in　time　of　flight　and　amplitude　of　the　guided　wave　signal　during　cycling,　which　correctly　validates　the　range　of　theoretical　time　of　flight.　Furthermore,　the　applicability　of　the　proposed　method　is　verified　by　battery　experiments　with　different　temperature　and　current　rate　operating　conditions.　Furthermore,　the　ultrasonic　guided　wave　detection　approach　has　also　been　shown　to　be　a　sensitive　means　of　determining　the　SOC　of　lithium-ion　batteries.