In　this　paper,　the　vibration　characteristics　of　the　cantilever　rectangular　plate　with　side　crack　are　studied　in　the　way　of　analysis,　which　including　natural　frequency　and　mode　shape.　The　influences　of　different　parameters　of　crack,　such　as　the　locations　and　lengths　of　crack,　to　the　vibration　characteristics　of　the　cantilever　rectangular　plate　are　investigated.　The　modal　function　of　the　crack　plate　consists　two　parts,　which　are　(1)　the　modal　function　of　intact　cantilever　rectangular　plate　from　beam　functions　combination　method　and　(2)　corner　functions　presenting　the　discontinuity　of　displacement　and　slope　along　the　crack.　The　natural　frequencies　and　modal　shapes　can　be　obtained　when　taking　the　modal　function　into　the　method　of　Ritz.　At　last,　the　effects　of　the　crack　location　and　crack　length　on　the　vibration　characteristics　are　investigated,　and　it　could　provide　the　theoretical　basis　for　engineering　application　and　the　relevant　study.