Over　the　past　twenty　years,　urban　spatial　areas　in　China　have　expanded　in　an　accelerated　speed　with　the　China＇s　economic　reform.　This　causes　the　conversion　of　the　vegetated　lands　into　built-up　lands　and　thus　has　significant　impacts　on　the　ecosystem,　biodiversity　and　local　climate.　Quanzhou,　Jinjiang　and　Shishi　are　three　cities　located　in　the　Jinjiang　estuary　lowland　area　of　southeast　Fujian　Province　and　are　famous　for　their　fast　economic　development.　In　the　meantime,　the　urban　areas　of　the　cities　have　been　growing　rapidly.　To　study　the　dynamics　of　the　urban　expansion　for　recent　20　years,　multi-temporal　Landsat　TM　images　of　1987,　1996　and　2006　were　used.　The　mapping　of　the　urban　extent　was　assisted　by　the　Index-based　Built-up　Index　(IBI)　through　enhancing　built-up　land　features　in　the　images.　The　multi-temporal　analysis　reveals　that　the　total　urban　area　of　the　three　cities　has　greatly　increased.　This　resulted　in　the　development　of　the　urban　heat　island.　The　regression　statistics　indicate　that　the　built-up　land　has　a　positive　exponential　relationship　with　the　land　surface　temperature　(LST).　Therefore,　the　increase　in　built-up　land　percentage　can　exponentially　accelerate　the　rise　of　the　LST.　©　2008　IEEE.