The　discrete　finite　element　(FE)　model　often　cannot　reflect　structure　characteristics　accurately　due　to　imply　more　idealistic　assumptions　and　simplifications.　Therefore,　it　is　necessary　to　update　FE　model　for　structural　damage　identification,　response　calculation,　safety　evaluation,　optimization　design,　and　so　on.　This　article　will　illustrate　respectively　three　key　steps　of　updating　parameters　selection,　target　function　selection　and　optimization　method　in　process　of　dynamic　FE　model　updating　of　footbridge　structures　based　on　ambient　excitation,　and　put　forward　a　feasible　updating　method:　combine　empirical　method　with　sensitivity　analysis　method　to　select　updating　parameters;　joint　natural　frequencies,　MAC　and　modal　flexibility　as　target　function;　adopt　optimization　algorithm　based　on　the　optimization　theory.