Based　on　reconstruction　and　extension　works　of　the　Dongchangyu　tunnel,　the　tunnel　blasting　excavation　technology　under　multi-free　face　is　studied　by　following　the　characteristics　of　the　bifurcating　and　separating　of　the　reconstructed　tunnel　section　from　the　existing　one,　and　the　tunnel　section　with　vault　cavity　is　selected　as　a　typical　cross-section　to　design　the　blasting　parameters　rationally.　Meanwhile,　through　blasting　vibration　monitoring　on　both　sides　of　the　existing　tunnel,　the　characteristics　of　blasting　vibration　and　its　propagation　law　in　the　existing　tunnel　are　analyzed.　Research　results　can　provide　a　basis　for　adjusting　the　tunnel　blasting　parameters　and　selecting　the　support　type　to　the　cavity　section.　©,　2015,　Editorial　Office　of　＇Modern　Tunnelling　Technology＇.　All　right　reserved.