A　variable　friction　system　with　normal　pressure　changeable　was　presented,　where　the　frictional　force　of　the　system　can　be　increased　with　the　increase　of　displacement　of　the　system.　The　new　system　can　be　used　in　TMD　to　avoid　the　disadvantage　of　invariable　friction　TMD.　Using　first　order　harmonic　balance　method,　the　equivalent　damping　ratio　and　frequency　of　SDOF　variable　friction　system　were　deduced　and　analyzed.　The　frequency　response　characteristics　of　SDOF　variable　friction　system　were　discussed　by　comparing　with　SDOF　classical　damping　system.　The　control　effectiveness　of　variable　friction　TMD　under　harmonic　excitation　was　inspected　theoretically　and　experimentally.　The　results　demonstrates　that　the　frequency　response　characteristics　of　variable　friction　TMD　and　classically　damping　TMD　are　similar　and　both　can　effectively　reduce　structural　response　under　harmonic　excitation.