The　urban　development　is　usually　accompanied　with　the　re-planning　and　reconstruction　of　the　old　urban　area,　which　is　one　of　the　key　issues　of　the　urban　development　program.　Over　the　past　decade,　Fuzhou　City　of　Fujian　province,　SE　China,　has　speeded　up　its　reconstruction　progress.　The　Cangxia　area,　located　in　the　southwestern　of　the　city,　was　re-planed　and　reconstructed　to　improve　people＇s　living　conditions　because　the　area　was　full　of　intensively-built　squatter　settlements.　In　order　to　study　the　thermal　environmental　changes　of　the　Cangxia　area　before　and　after　the　reconstruction,　three　Landsat　TM　images　of　1986,　1996　and　2006　were　utilized　to　perform　feature　extractions　of　the　thermal-related　information　of　the　area,　such　as　the　land　surface　temperature　(LST),　impervious　surface　area　(ISA)　and　vegetation　coverage.　The　quantitative　analysis　on　the　relationship　between　ISA　and　LST　suggested　a　positive　exponential　relationship　between　the　two　factors.　With　the　assistance　of　the　Urban-Heat-Island　Ratio　Index　(URI),　the　digital　image　processing　on　the　three　multi-temporal　images　revealed　the　spatial　and　temporal　variations　of　the　urban　heat　island　(UHI)　effect　in　the　investigated　area　from　1986　to　2006.　The　results　showed　that　after　the　launch　of　the　reconstruction　project　of　this　squatter　settlement-dominated　area,　the　UHI　effect　in　the　area　had　been　greatly　mitigated　in　the　past　20　years,　since　the　URI　value　had　been　decreased　from　0.648　in　1986　to　0.245　in　2006.　This　owes　greatly　to　the　significant　decrease　in　high-density　ISAs　and　the　notable　increase　in　vegetation　covers.　The　reconstruction　is　of　benefit　to　the　UHI　mitigation　of　the　Cangxia　area.