Abstract: Quantitative research and analysis of the ecosystem services value (ESV) change and ecological security pattern in Chengdu-Deyang-Mianyang (CDM) city belt are crucial for cross-administrative coordination to build an ecological security barrier, strengthen ecosystem protection, advance the ecological restoration planning, and promote the construction of ecological civilization. The spatial and temporal variations of ESV in CDM city belt from 2010 to 2018 were analyzed using ESV equivalence method. Then, 99%, 95% and 90% confidence level ESV hotspots in the region were extracted and the core "source" ecological protection areas were identified. Eight important resistance factors such as elevation and land use were selected to obtain the resistance surface, and the minimal cumulative resistance model was used to construct the regional ecological corridors and identify the ecological security patterns in urban belts. The optimization suggestions of the spatial layout of ecological networks across administrations were proposed. The results showed that from 2010 to 2018, the total value of ecosystem services in the study area increased from 137.291 billion to 151.993 billion, with growth rates above 10 percent for raw materials, gas regulation, climate regulation, waste disposal, soil formation and conservation, and biodiversity conservation. The ecological safety level of the study area showed a spatial distribution characterized by a high level in the northwest and a low level in the southeast, 49.8% of which were with the highest and second-highest safety levels and concentrated in the northwest, south-central and other regions. The medium- and low-security zones accounted for 50.2 percent of the total, mainly concentrated in low-altitude urban areas such as construction sites in the south. 24 ecological "source" sites were identified, accounting for 27.3% of the total area of the study area, and were distributed in a zonal pattern; fifty-three ecological corridors and forty-one ecological nodes were identified, showing an overall polycentric ring shape and an excellent overall level of network connectivity. Based on the research results, the spatial structure of the ecological network of "two axes, three belts and four nodes" was constructed in the northwest (dense) and southeast (sparse), which provided references and suggestions for regional ecological security.