This　study　investigates　the　prestress　loss　and　thermal　expansion　performance　of　steel　cables　under　high　temperatures.　The　calculation　formula　of　cable　prestress　loss　is　first　deduced　theoretically.　The　prestress　loss　value　of　cable　under　force-thermal　coupling　is　then　obtained　through　numerical　simulation　and　is　compared　with　the　calculation　results　of　the　theoretical　formula.　Theoretical　deduction　is　then　employed　to　determine　the　relationship　between　the　thermal　expansion　coefficient　of　the　cable　and　wire　in　the　unstressed　state.　A　numerical　analysis　model　is　established　to　simulate　the　mechanical　properties　of　the　cable　in　an　unstressed　state.　The　results　show　that　the　thermal　expansion　coefficient　of　the　cable　in　an　unstressed　state　is　the　same　as　that　of　steel　wire.　Finally,　considering　that　the　cable　is　in　the　stress　state　in　an　actual　structure,　the　high-temperature　prestress　loss　of　steel　cables　under　force-thermal　coupling　is　obtained　through　simulation　analysis.　The　equivalent　thermal　expansion　coefficient　is　then　calculated,　and　the　influence　of　different　twist　angles,　steel　wire　layers,　initial　prestress,　section　type,　and　cable　length　on　the　equivalent　thermal　expansion　coefficient　of　steel　cables　is　determined.