The　ground　micro-tremor　signals　observed　in　coastal　area　of　Fujian　Province　were　analyzed　and　processed　by　fast　Fourier　transform　(FFT)　method.　The　indicatrixes　of　physical　and　mechanical　properties　of　ground　soil　were　also　tested　by　combining　indoor　test　with　in-situ　one.　The　formation　mechanism　and　propagating　characteristics　of　ground　micro-tremor　were　studied,　which　was　confirmed　by　earthquake　damages.　The　conclusions　obtained　are　as　follows:　First,　the　equivalent　shear　wave　in　overburden　layer　is　one　main　factor　affecting　the　predominant　period　of　ground　micro-tremor.　Second,　the　thickness　of　overburden　layer,　soft　soil　and　its　stiffness　are　three　other　important　factors　affecting　the　predominant　period　of　ground　micro-tremor.　Third,　the　relationship　between　the　predominant　period　of　ground　micro-tremor　and　the　shear　wave　propagation　time　in　the　overburden　layer　is　closely　related.　Fourth,　the　propagating　time　of　shear　wave　in　overburden　layer　can　better　reflect　the　change　of　predominant　period　of　ground　micro-tremor,　and　vice　versa.　Fifth,　the　results　indirectly　reveal　quantitatively　that　ground　micro-tremor　is　one　of　body　waves　that　is　mainly　a　shear　wave,　which　backs　the　theory　on　body-wave　cause　of　ground　micro-tremor　formation.