Understanding　the　evolution　and　driving　factors　of　sedimentation　and　erosion　at　the　mouths　of　small　and　medium-sized　mountain　streams　during　various　periods　is　essential　for　regional　spatial　utilization,　development,　and　sustainable　economic　growth.　This　is　particularly　important　when　considering　the　combined　impact　of　climate　change　and　human　activities.　This　paper　presents　an　analysis　of　the　changes　in　sedimentation　and　erosion　of　mouth　isobaths　and　underwater　deltas　over　different　periods　using　nautical　chart　data　(1950-2019)　and　analyzes　the　factors　driving　changes　in　sedimentation　and　erosion　during　different　periods　from　1950　to　2020　based　on　the　runoff-sediment　discharge　of　the　Minjiang　River　(MR)　and　extreme　climate　factors　such　as　typhoons,　especially　the　driving　factors　that　caused　a　sudden　change　in　the　sedimentation　and　erosion　process　between　1998　and　2005.　The　results　indicate　that　runoff-sediment　characteristics　are　crucial　in　driving　sedimentation　and　erosion　changes.　In　the　past　70　years,　the　underwater　delta　of　the　MRE　has　mainly　experienced　four　stages:　deposition　(1950-1992)　-erosion　(1993-1998)　-deposition　(1998-2011)　-erosion　(2011-2019).　Taking　the　impoundment　operation　of　the　Shuikou　Reservoir　in　1993　as　the　node,　the　sediment　load　of　the　Minjiang　River　into　the　sea　began　to　decrease　sharply,　and　then　the　estuary　quickly　showed　a　state　of　erosion.　The　change　of　sediment　flux　into　the　sea　is　the　main　driving　factor　for　the　evolution　of　erosion　and　deposition　in　the　Minjiang　River　Estuary　(MRE).　The　critical　value　of　the　erosion-deposition　transition　is　about　570.3　x　104　t/yr.　After　the　estuary　entered　a　state　of　erosion　in　1993-1998,　significant　siltation　suddenly　occurred　in　1998-2005.　The　reason　for　the　siltation　in　this　period　may　be　related　to　the　frequent　transit　typhoons　and　flood　events　in　1998-2005.　Therefore,　the　change　of　river　sediment　supply　into　the　sea　is　the　main　driving　factor　controlling　the　erosion　and　deposition　evolution　of　the　Minjiang　River　estuary　on　a　long　time　scale　of　more　than　10　years,　which　reflects　the　influence　of　large-scale　human　activities　on　the　river　and　estuary　area　in　the　past　half　century.　Extreme　climate　events　are　the　incentive　to　adjust　the　estuary　landform　in　the　short　term.　Extreme　climate　events　will　not　fundamentally　change　the　process　of　estuarine　geomorphological　evolution　under　the　background　of　sediment　supply　reduction.