[Objective] The ecological environment quality in Alar reclamation area was evaluated with the help of remote sensing ecological index (RSEI), to analyze the changes and driving factors of ecological environment in the study area in recent 30 years, in order to provide scientific reference for the development and ecological protection of Alar reclamation area. [Methods] Landsat TM/ETM⁺/OLI image data in 1990, 2000, 2011 and 2020 were selected to construct RSEI by coupling green index (NDVI), humidity index (WET), dryness index (NDSI) and heat index (LST). The driving factors such as climate, population and economy were considered to explore the dynamic changes of eco-environmental quality in Alar reclamation area. [Results] The average value of RSEI in Alar reclamation area increased from 0.344 to 0.468 during 1990—2020, and the ecological environment quality was generally improved. From 1990 to 2020, the quality of ecological environment in the Alar reclamation area improved mainly in the northern and southern areas. The improved area reached to 1 756.36 km², accounting for 45.92% of the total area. The ecological environment quality was affected by natural factors and socio-economic factors. Changes in the quality of the ecological environment in the Erken area played a leading role. [Conclusion] the ecological environment in Alar reclamation area has been effectively improved in recent 30 years, and the remote sensing ecological index can effectively reflect the changes of ecological environment quality in Alar reclamation area.