Background A good ecological environment is not only the most important premise of human development, but also the basic guarantee of human survival and the basis of social development. Coastal cities are rich in resources and have intense economic and social activities. Exploring the temporal and spatial change pattern and distribution law of their ecological quality is conducive to promoting the ecological environment protection and governance of coastal cities.

Methods We extracted greenness (normalized difference vegetation index, NDVI), humidity (wetness, WET), dryness (normalized difference build and soil index, NDBSI) and heat (land surface temperature, LST) indexes from remote sensing images of Qingdao in 2005, 2009, 2014 and 2019, and constructed a remote sensing ecological index of Qingdao remote sensing based ecological index (RSEI) model. Further, we studied the temporal and spatial variation characteristics of ecological quality.

Results The average I of Qingdao city in 2005, 2009, 2014 and 2019 were 0.433, 0.468, 0.470 and 0.578, respectively, and the overall ecological environment quality showed an upward trend. The proportions of areas with excellent ecological environment quality increased from 5.82% in 2005 to 6.14% in 2009, 15.93% in 2014 and 42.26% in 2019, respectively. The proportions of areas with poor ecological environment quality decreased from 39.1% in 2005 to 22.73% in 2009, 4.18% in 2014 and 1.79% in 2019 respectively. The ecological environment quality of Qingdao city was better in suburb than in central city. The eco-environmental grade was mainly medium and good. The deterioration of ecological environment quality was concentrated in the northern and western coastal areas of Jiaozhou city. The areas with improved eco-environmental quality were mainly distributed in Jimo city, the north of Laixi city and Pingdu city. The improvement and deterioration of ecological environment quality accounted for 64.43% and 1.87% of the total area. The average correlation coefficient between RSEI model and each component index were 0.803, which were higher than the average correlation coefficient between each component index. Among them, WET and NDVI had the greatest impact on the ecological quality of Qingdao city, followed by NDBSI, and LST has the least impact.

Conclusions The RSEI model can better reflect the information of each component index, accurately characterize the changes of environmental quality of soil and water conservation ecological restoration in Qingdao city, which provide reference and guidance for the ecological restoration, treatment and development of coastal zone in Qingdao city.