It　is　of　great　significance　to　grasp　the　spatio-temporal　characteristics　and　expansion　mechanism　of　urban　built-up　areas　for　formulating　urban　development　strategy.　This　paper　takes　the　built-up　area　of　Fuzhou　as　the　study　area,　uses　multi-temporal　Landsat　images　and　remote　sensing　data　of　nighttime　light　(NTL)　as　the　main　data　sources,　and　extracts　the　built-up　area　of　NTL　images　with　a　higher　spatial　resolution　comparison　method.　It　discusses　the　development　trends　of　the　Fuzhou　built-up　area　from　2000　to　2021　from　the　perspectives　of　temporal　and　spatial　evolution　characteristics　and　spatial　morphology　evolution　and　analyzes　the　relationship　between　population　factors,　economic　factors,　natural　conditions,　policy　factors,　and　urban　expansion.　The　results　show　that　the　urbanization　level　of　Fuzhou　is　gradually　improving,　and　the　compounded　nighttime　light　index　(CNLI)　increases　from　0.0105　in　2000　to　0.0635　in　2021.　The　trend　of　expansion　speed　and　expansion　intensity　is　consistent,　showing　the　changing　trend　of　first　fast　and　then　slow,　then　accelerating　and　then　slowing　down.　The　expansion　direction　presents　the　trend　of　＂expanding　eastward,　advancing　southward　and　expanding　westward＂,　the　spatial　form　tends　to　be　irregular,　and　the　migration　range　of　the　center　of　gravity　is　not　significant.　Population　factors,　economic　factors,　and　expansion　are　positively　correlated　and　closely　related,　and　natural　conditions　and　policy　guidance　affect　the　direction　and　mode　of　the　expansion　of　the　built-up　area.　The　above　results　indicate　that　the　overall　urban　development　of　Fuzhou　shows　an　upward　trend,　which　is　consistent　with　the　planned　urbanization　development　trend　of　Fuzhou.