To　improve　the　excitation　and　reception　performance　of　surface　wave　EMAT　and　increase　the　accuracy　for　quantitative　defect　detection,　the　influence　of　wire　length　in　meander-line-coil　on　the　frequency　characteristic,　acoustic　beam　directivity　and　attenuation　were　studied　experimentally.　Meander-line-coils　with　different　wire　lengths　were　used　to　detect　the　artificial　cracks,　the　reflection　and　transmission　coefficients　of　surface　wave　were　obtained,　and　the　influence　of　the　relation　between　wire　length　and　crack　length　on　quantitative　detection　of　defect　was　analyzed.　Results　show　that　the　frequency　characteristic　is　independent　of　wire　length,　while　the　beam　directivity　and　attenuation　of　surface　waves　are　closely　related　to　it.　With　the　increase　of　wire　length,　the　radiation　half　angle　of　surface　waves　beam　decreases　and　the　attenuation　slows　down.　The　space　resolution　of　EMAT　is　reduced　and　the　SNR　of　received　signal　increases　with　the　increase　of　wire　length　when　the　EMAT　is　used　as　a　receiver.　The　reflection　and　transmission　coefficients　can　be　measured　accurately　only　when　the　wire　length　of　meander-line-coils　is　smaller　than　the　crack　length.　©　2018,　Editorial　Department　of　Journal　of　Beijing　University　of　Technology.　All　right　reserved.