Rapid urbanization poses a serious threat to the ecological environment in the fragile karst mountainous cities. Systematic monitoring and evaluation of urban land use/cover pattern changes and its ecological effects, and coordination between ecological protection and urban development are important propositions for the construction of demonstration cities of ecological civilization in karst mountainous cities. Taking Huaxi District of Guiyang City as the object, Landsat ETM/OLI remote sensing images in 2013 and 2018 were the main data source. Based on remote sensing and GIS technology and using remote sensing ecological index (RSEI) model, the land use/cover types and eco-environment quality were systematically analyzed, and the ecological effects of land use/cover change were accessed. The results show that:(1) The land use/cover pattern of Huaxi District has changed significantly from 2013 to 2018. The cultivated land was decreased nearly 15353.37 hm², and 90% of the transferred cultivated land were converted to construction land or woodland and/or shrubbery land, accompanied by partial forest land degradation (2683.80 hm²), which formed a pattern dominated by woodland, construction land and cultivated land types. (2) In the past five years, the ecological environment quality in Huaxi District showed a downward trend with RSEI value decreased from 0.622 in 2013 to 0.499 in 2018. The greenness index and dryness index were the most contribution factors to the quality of ecological environment in Huaxi District. (3) The spatial distribution and change of land use/cover and ecological environment quality were coincided with each other. The increase or decrease of forest land or forest land and shrub land area had the significant impact on the change of ecological environment quality. The 10% increase of forest land or forest land+shrub land area could increase the area of ecological quality improvement by 15%-20%, or reduce the area of ecological quality deterioration by 4%. However, the forest land degradation area increased by 10% might lead to the ecological quality deterioration area increased by about 14%. The research can provide scientific basis for the optimization of land use space pattern, the improvement of urban ecological environment, and the construction of ecologically civilized cities in karst mountainous cities.