The　dynamic　stability　of　vortex-induced　vibration　(VIV)　of　circular　cylinders　has　been　well　investigated.　However,　there　have　been　few　studies　on　this　topic　for　bridge　decks.　To　fill　this　gap,　this　study　focuses　on　the　dynamic　stability　of　a　VIV　system　for　bridge　decks.　Some　recently　developed　techniques　for　nonlinear　dynamics　are　adopted,　for　example,　the　state　space　reconstruction　and　Poincare　mapping　techniques.　The　dynamic　stability　of　the　VIV　system　is　assessed　by　combining　analytical　and　experimental　approaches,　and　a　typical　bridge　deck　is　analyzed　as　a　case　study.　Results　indicate　that　the　experimentally　observed　hysteresis　phenomenon　corresponds　to　the　occurrence　of　saddle-node　bifurcation　of　the　VIV　system.　Through　the　method　proposed　in　this　study,　the　evolution　of　dynamic　stability　of　the　VIV　system　versus　wind　velocity　is　established.　The　dynamic　characteristics　of　the　system　are　further　clarified,　which　offers　a　useful　clue　to　understanding　the　VIV　system　for　bridge　decks,　while　providing　valuable　information　for　mathematical　modeling.