Abstract: Haicheng-Dashiqiao area in Liaoning Province is the largest magnesite base in China.Open-pit mining makes the surrounding ecological environment severe.In order to better develop mines and protect regional ecology, this paper monitors and evaluates their environmental quality.Landsat remote sensing images in 1984, 1990, 2007, 2010 and 2016 are selected to extract four ecological factors, namely greenness, humidity, dryness and heat.The remote sensing ecological index (RSEI)model is constructed by principal component analysis, and combined with land use to analyze the evolution of ecological environment in the study area.Combined with the change of land use types, the ecological environment evolution of the study area is analyzed.The results show that the average value of RSEI increased first, then decreased and then increased from 1984 to 2016.The grading results of RSEI value show that the regions with poor ecological quality increased first and then decreased.The regions with excellent ecological environment quality show a fluctuating upward trend.The area with good ecological quality is the largest.Combined with RSEI value classification and land use classification, the main reasons for the deterioration of ecological environment in the study area are as follows.Firstly, the scale of urbanization has expanded, and forest land and cultivated land have been occupied or forest land has been transformed into cultivated land.Secondly, the open-pit mining and dump of magnesite have affected the mining environment.The improvement of ecological environment in the later period is due to reclamation and afforestation in mining areas, which increases the area of forest land, improves the environmental quality and has achieved remarkable results in environmental governance.This study can provide a scientific basis for ecological monitoring and treatment in open-pit mining areas.