The　threshold　control　of　safety　blasting　vibration　velocity　is　a　significant　process　for　the　underground　mining　of　complicated　ore　deposit　under　construction,　road,　and　water.　According　to　the　equivalent　principle　of　displacement　and　velocity　of　mass　point,　differential　evolution　is　put　forward　based　on　3DEC　dynamic　analysis,　making　the　calculation　more　efficient　and　accurate.　The　3DEC　model　of　the　complicated　orebody　under　railway　is　established　according　to　the　topographic　maps　and　geological　data　of　the　eastern　Pyrite　Mine.　The　stimulus-response　distribution　of　internal　stress　and　displacement　fields　are　demonstrated　by　analyzing　the　on-site　monitoring　vibration　displacement　and　velocity　data　of　the　mass　point.　The　reliability　of　parameter　selection,　such　as　blasting　simulation　waveforms,　rock　damping,　is　identified.　The　safety　vibration　velocity　of　railway　is　set　to　4.5　cm/s　in　line　with　the　requirement　of　safety　blasting　rules.　Thus,　the　maximum　amount　of　single-stage　explosive　in　this　region　is　44.978　kg.　The　simulation　result　is　in　good　agreement　with　the　on-site　monitoring　datum.　No　displacement　and　settlement　of　the　701　railway　special　line　was　achieved　by　choosing　the　critical　amount　of　the　single-stage　explosive.　©　2011,　China　University　of　Mining　&　Technology.　All　rights　reserved.