To　solve　the　contact　defect　(such　as　cracks,　delaminations)　detection　in　structures,　a　nonlinear　acoustic　technique　for　detection　of　contact　defects　in　plates　using　sparsely　distributed　sensors　was　developed　associating　guided　waves　with　vibro-modulation　techniques.　The　low　frequency　vibration　varies　the　interface　area　within　the　contact　defect;　therefore　the　amplitude　and　phase　of　high　frequency　guided　waves　reflected　from　the　contact　defect　will　be　modulated.　Due　to　the　exiting　of　contact　defects,　there　is　obvious　low　frequency　component　in　the　time-frequency　distribution　of　modulated　guided　wave　series.　Furthermore　the　nonlinear　responses　at　frequency　of　vibration　are　extracted　out　and　used　for　defect　imaging.　It　is　shown　that　the　nonlinear　guided　wave　imaging　method　based　on　vibration　modulation　can　effectively　characterize　and　locate　the　nonlinear　contact　defects.