A　new　type　of　velocity-adjustable　semi-active　TMD　is　presented.　Velocity-adjusting　devices　consist　of　impulse　generators　and　clutches.　Impulse　is　generated　by　joint　operation　of　electromagnets　and　springs.　MR　dampers　are　used　as　clutches.　According　to　the　working　mechanism　of　TMD,　rules　of　adjusting　velocity　are　established.　The　analysis　program　is　developed　in　the　VB　platform.　Seismic　response　of　SDOF　structures　with　passive　TMD　and　velocity-adjusting　TMD　are　analyzed.　From　the　analysis　results,　it　can　be　concluded　that　(1)　the　control　effect　of　a　normal　passive　TMD　greatly　depends　on　the　characteristics　of　ground　motion　and　structures　and　sometimes　not　so　good;　(2)　the　control　effectiveness　of　the　proposed　semi-active　TMD　is　much　better　than　that　of　the　normal　TMD　under　typical　earthquake　acceleration　recordings;　(3)　Unlike　other　TMD　system,　the　proposed　semi-active　TMD　still　has　good　a　control　effectiveness　when　the　primary　structure　enters　into　plastic　working　state　during　severe　earthquake.　The　proposed　device　also　has　following　ad　vantages,　i.e.,　working　mechanism　reasonable,　control　algorithm　simple,　hardware　feasible　and　less　energy　consumption.