In　this　paper,　the　physical　model　of　the　cantilever　beam　with　a　surface　crack　is　established　to　study　the　free　vibration　of　the　cracked　beam　from　three　aspects　that　are　theoretical　analysis,　FEM　analysis,　and　experiment.　At　the　same　time,　the　relation　between　the　crack　parameter　and　the　vibration　characteristics,　which　are　natural　frequencies　and　the　modes　of　each　order,　is　obtained　through　analysis.　The　theoretical　analysis　is　on　the　basis　of　the　mode　analysis　theory　and　applied　mechanics.　The　crack　is　regarded　as　a　flexible　hinge.　Utilizing　the　external　boundary　conditions　and　internal　boundary　conditions　at　the　crack,　the　free　vibration　characteristics　are　obtained　combining　with　the　vibration　mechanics.　With　the　ANSYS　software,　a　finite　element　model　of　the　cracked　beam　is　established　by　the　beam　element.　During　the　process　of　calculation,　it　calculates　the　natural　frequencies　and　the　modes　of　cracked　beam　with　different　parameters　of　crack.　The　results　obtained　from　the　experiment　are　in　agreement　with　the　results　obtained　from　the　theoretical　and　the　FEM　analysis.　So　the　accuracy　of　the　theoretical　analysis　and　the　numerical　simulation　is　verified　by　the　experiment.　At　last,　the　effects　of　the　crack　location　and　depth　on　the　natural　frequencies　and　modes　of　each　order　are　shown,　and　it　could　provide　the　theoretical,　numerical　and　experimental　basis　for　the　identification　of　cracked　materials　and　the　relevant　study.　©　(2013)　Trans　Tech　Publications,　Switzerland.