Transmission　tower-line　system　is　one　of　most　critical　lifeline　systems　to　cities.　However,　it　is　found　that　the　transmission　tower-line　system　is　prone　to　be　damaged　by　earthquakes　in　past　decades.　To　mitigate　seismic　demands,　this　study　introduces　a　tuned-mass　damper　(TMD)　using　superelastic　shape　memory　alloy　(SMA)　spring　for　the　system.　In　addition,　considering　the　dynamic　characteristics　of　both　tower-line　system　and　SMA　are　affected　by　temperature　change.　Particular　attention　is　paid　on　the　effect　of　temperature　variation　on　seismic　behavior.　In　doing　so,　the　SMA-TMD　is　installed　into　the　system,　and　its　properties　are　optimized　through　parametric　analyses.　The　considered　temperature　range　is　from　-40　to　40　degrees　C.　The　seismic　control　effect　of　using　SMA-TMD　is　investigated　under　the　considered　temperatures.　Interested　seismic　performance　indices　include　peak　displacement　and　peak　acceleration　at　the　tower　top　and　the　height-wise　deformation.　Parametric　analyses　on　seismic　intensity　and　frequency　ratio　were　carried　out　as　well.　This　study　indicates　that　the　nonlinear　behavior　of　SMA-TMD　is　critical　to　the　control　effect,　and　proper　tuning　before　application　is　advisable.　Seismic　demand　mitigation　is　always　achieved　in　this　wide　temperature　range,　and　the　control　effect　is　increased　at　high　temperatures.