Severe　soil　loss　has　caused　ecological　degradation　for　the　global　ecosystem,　thus　it　is　a　major　problem　facing　the　world　today.　Timely　and　fast　monitoring　ecological　changes　in　soil　loss　regions　has　become　an　increasing　concern.　This　paper　develops　a　remote　sensing　assessment　method　of　soil　erosion-induced　changes　in　regional　ecological　quality　based　ecological　index　(RSEI).　The　proposed　index　combines　four　indicators　from　existing　remote-sensing　indices/components　to　represent　greenness,　dryness,　wetness　and　heat,　which　are　the　important　ecological　indicators　frequently　used　in　assessing　regional　ecological　status.　The　four　remote-sensing　indices/components　are　the　normalized　difference　vegetation　index　(NDVI),　soil　index　(SI),　wetness　component　of　the　tasseled　cap　transformation　(Wet),　and　land　surface　temperature　(LST).　The　principal　component　analysis　(PCA)　was　utilized　to　compress　the　four　indicators　into　one　index　-　RSEI,　in　order　to　assess　overall　ecological　status.　The　new　index,　RSEI,　was　thus　constructed　using　the　first　component　as　it　was　proved　to　have　effectively　combined　the　most　information　of　the　four　indicators.　The　application　of　the　RSEI　in　Hetian　basin　area　in　Changting　county　of　Fujian　province,　one　of　the　most　serious　reddish　soil　erosion　areas　in　southern　China,　showed　that　the　RSEI　can　quantitatively　assess　the　ecological　effects　of　soil　loss　treatment　in　the　area　and　easily　detect　spatial　and　temporal　changes　of　the　ecological　quality　through　a　time　period　from　1988　to　2010.　The　application　utilized　three　Landsat　TM　images　of　1988,　2004　and　2010.　The　four　indicators　(NDVI,　SI,　Wet　and　LST)　of　each　year　were　retrieved　from　the　images　and　then　combined　through　the　PCA　transform　to　form　the　RSEIs　for　the　study　years.　The　RSEI-based　analysis　indicated　that　after　a　more　than　20　years　fight　for　soil　loss　in　the　area　by　the　local　people　and　government,　the　ecological　quality　of　the　area　has　been　significantly　improved.　This　is　suggested　by　an　increase　in　the　mean　RSEI　value　from　0.5　in　1988　to　0.59　in　2010,　accompanied　by　a　decrease　in　low　level　RSEI　area　from　66.1%　to　47.7%,　and　an　increase　of　high　level　RSEI　area　from　33.9%　to　52.3%　in　this　duration.　Quantitative　analysis　reveals　that　the　greenness　indicator　represented　by　NDVI　contributes　most　to　the　RSEI　change　among　the　four　indicators　used　for　generating　the　index.　This　suggests　that　the　biological　restore　of　soil　erosion　areas　by　planting　tree　and　grass　is　an　effective　way　to　soil-erosion　treatment　for　Hetian　basin.