A　distributed　optical　fiber　vibration　sensor　based　on　Sagnac　interferometer　is　developed　in　this　paper,　and　it　is　used　to　detect　pipeline　leakage　in　real-time.　The　Principle　of　sensor　and　phase　modulation　theory　of　light　are　discussed.　A　simulation　experiment　is　designed　to　verify　the　distributed　optical　fiber　vibration　sensor,　the　results　verify　that　the　detection　technology　can　effectively　detect　vibrating　signals.