Due　to　the　problem　that　the　tuned　mass　damper　(TMD)　system　is　easy　to　be　off-tuned　when　applied　to　light　structures,　which　leads　to　the　decline　of　vibration　reduction　effect,　a　new　shape　memory　alloy　semi-active　TMD　system　is　designed　in　this　paper.　The　system　uses　steel　cables　to　suspend　the　mass　to　bear　all　its　weight.　Large　shape　memory　alloy　bars　with　rectangular　effective　cross　sections　are　used　to　provide　different　bending　stiffness　in　the　two　directions　of　the　TMD　system　in　the　horizontal　plane.　In　order　to　study　the　semi-active　performance　of　the　system,　a　full-scale　shape　memory　alloy　TMD　system　was　subjected　to　free　vibration　tests　in　this　paper.　By　changing　the　working　temperature　of　the　shape　memory　alloy,　the　influence　of　temperature　change　on　the　frequency　and　damping　ratio　of　the　TMD　system　was　studied.　The　test　results　show　that　by　controlling　the　working　temperature　of　the　shape　memory　alloy　from　-40　益　to　80　益,　the　frequency　of　the　TMD　system　shows　an　increasing　trend　with　temperature　increases,　while　the　damping　ratio　shows　a　decreasing　trend　with　the　temperature　increases.　The　results　show　that　the　new　shape　memory　alloy　semi-active　TMD　system　is　applied　to　controlled　structures,　and　once　the　TMD　is　off-tuned,　it　can　be　re-tuned　by　changing　the　temperature　of　the　shape　memory　alloy.　Therefore,　the　new　shape　memory　alloy　TMD　system　designed　in　this　paper　has　certain　engineering　application　value　and　prospect　for　the　study　of　light　structure　vibration　reduction.　©　2024　Editorial　office　of　Earthquake　Engineering　and　Engineering　Dynamics.　All　rights　reserved.