Ecological protection and high-quality development in the Yellow River Basin are major national strategies. Construction of county-level ecological security pattern and the quantitative diagnosis of ecological problems are the basic units for implementing ecological protection and restoration. Taking Shenmu City as the research object, this paper firstly constructed the ecological security pattern of Shenmu City based on circuit theory, and took the identified ecological pinch points, ecological barrier points and low-quality ecological spaces as key areas for ecological restoration. Secondly, the existing ecological problems in the key areas of ecological restoration were quantitatively diagnosed. Finally, the key areas of ecological restoration zones were delineated through the calculation results of the ecological problem index (EPI). The result showed that:(1) the ecological sources' area of Shenmu City was 411.64 km², mainly being grassland distributed in the central, eastern and southern regions. There were 63 ecological corridors between the ecological sources, with a total length of about 610.71 km, which were denser in the central region than those in the southeast. (2) The key areas of ecological restoration identification based on the ecological security pattern included 415 ecological pinch points with an area of 30.55 km², 341 ecological barrier points with an area of 25.72 km², and the area of low-quality ecological space with an area of 1043.73 km². (3) Soil erosion in the key areas of ecological restoration was mainly dominated by slight erosion. The geological disasters mostly occurred in mining areas and loess hilly and gully areas. Low-value areas of water conservation were mainly distributed in low-quality ecological spaces. The degradation degree of forests land and grassland was lower in the eastern than that in the middle and southwestern. The fragmentation degree of cultivated land was higher in the eastern and southeastern, but lower in the middle and southwestern. The areas with high desertification index were mainly distributed in the sandy land of low-quality ecological space. Some rivers, lakes, wetlands, and vegetation have been transformed to non-ecological land over time. (4) According to the EPI calculation results, the key areas of the ecological restoration could be further divided into ecological conservation areas, ecological improvement areas, key control areas and key restoration areas. In the future, the ecological restoration should be carried out according to the spatial distribution characteristics and land use status of each district. The research results provide a theoretical basis for the construction of ecological security patterns and quantitative diagnosis of ecological problems, and are of great significance for practicing the concept of green development and promoting ecological protection and high-quality development in the Yellow River Basin.