The expansion of protected area (PA) networks is necessary for countries and territories worldwide to conserve biodiversity, protect natural ecosystems and achieve sustainable development. However, challenges remain in expanding the PA network effectively, especially in regard to addressing priority conservation areas and balancing social development and ecological conservation. These problems are addressed in the “Ecological Conservation Redline” (ECR), an ambitious program launched in China to establish a comprehensive and large-scale conservation network. In this study, we presented a framework based on the ECR to guide PA network expansion, which identifies the areas requiring priority conservation and incorporates coordinated ecological conservation and social development. The framework consists of three steps: (1) design the network by identifying the hotspots of ecological function, ecological fragility and biodiversity, (2) transform the network from theory to practice through boundary verification, and (3) define a management policy with consideration of the livelihood of local communities. This framework was applied in Sichuan Province, China to demonstrate its effectiveness on expanding the PA network and improving conservation efforts. The framework provides important references for planning of PA networks and contributes to global expectations of effective environmental management.