In view of the decline of urban ecological environment quality caused by urban expansion, based on the Landsat8 OLI_TIRS satellite digital product image data of three time phases in 2014, 2016 and 2018, the changes of ecological environment quality in the central city of Tianjin, China, were evaluated and analyzed using remote sensing ecological index (RSEI). The results show that the RSEI has good applicability to the central urban area of Tianjin, which is characterized by high urbanisation, concentrated and compact urban housing, and can monitor environmental quality and also play an important role in the study of spatial changes. It is shown that the average values of the RSEI in the central urban area of Tianjin in 2014, 2016 and 2018 were 0.547, 0.463 and 0.478 respectively, and the RSEI geographically shows an inverted U-shaped trend of low-high-low from north to south and west to east. The correlation analysis of each index from the central urban area of Tianjin city shows that the normalized difference built-up and soil index (NDBSI) is the index that affects the quality of the ecological environment in the study area the most, with a high negative correlation with the eco-environmental quality, and is an important reference for the future improvement of the ecological environment in the central urban area of Tianjin. The successful demonstration in the central urban area of Tianjin shows that the application of RSEI remote sensing ecological index in the assessment of ecological environment quality can provide a positive reference for learning the urban ecological environment quality, monitoring and controlling the regional environment, and planning and constructing the city.