In　this　paper,　Lamb　wave　health　monitoring　in　plate　structure　for　detection　of　nonlinear　contact　scatter　is　conducted　using　vibration　modulation　technique.　The　low　frequency　vibration　varies　the　interface　area　within　the　contact　defect;　therefore　the　amplitude　and　phase　of　high　frequency　Lamb　waves　reflected　from　the　contact　defect　will　be　modulated.　By　time-frequency　analysis　of　modulated　Lamb　wave　series,　the　nonlinear　responses　at　frequency　of　vibration　are　extracted　out　and　used　for　defect　imaging.　It　was　shown　that　the　nonlinear　Lamb　wave　imaging　method　based　on　vibration　modulation　can　effectively　characterize　and　locate　the　nonlinear　contact　defects.