The　unproperly　control　of　friction　force　between　the　electrode　wire　and　director　tends　to　break　the　electrode　wire　and　exacerbate　the　vibration　of　electrode　wire　in　the　electrical　discharge　micro-hole　machining.　In　the　light　of　this　problem,　the　electrode　wire　is　simplified　to　the　Euler-Bernoulli　beam　to　establish　the　calculation　model　of　the　critical　friction　force　and　analysis　model　of　its　inherent　mode.　The　law　between　the　electrode　wire＇s　length　and　the　friction＇s　influence　on　the　natural　frequency　of　the　transverse　vibration　of　the　electrode　wire　is　analyzed　by　using　the　finite　element　method.　The　critical　frictional　force　of　electrode　wire　with　a　diameter　of　0.19　mm　is　calculated.　The　critical　speed　of　the　micro-feed　rotary　axis　is　further　determined.　The　conclusion　can　be　used　to　guide　the　selection　and　optimization　of　process　parameters　in　the　process　of　electrical　discharge　micro-hole　machining.　©　2019,　Editorial　Department　of　JVMD.　All　right　reserved.