The　characteristics　of　natural　frequency　change　of　dynamic　response　was　investigated　in　the　fatigue　process　for　deferent　tensile-shear　spot-welded　joints.　The　results　showed　that　the　natural　frequency　varies　non-linearly　with　the　fatigue　damage　fraction.　According　to　the　fatigue　behavior　and　the　characteristics　of　dynamic　response　frequency　change,　a　fatigue　damage　parameter　was　defined　by　the　change　of　natural　frequency　by　the　natural　frequency　non-linear　behavior　with　the　cycle　ratio.　The　proposed　fatigue　damage　parameter　can　describe　the　non-linear　fatigue　damage　behavior.　A　nonlinear　fatigue　damage　evolution　model　was　developed　by　the　continuum　fatigue　damage　theory.