For safeguarding ecological and agricultural land, the “Double Evaluation,” which integrates Resource and Environmental Carrying Capacity and Development Suitability, has become a fundamental component of territorial spatial planning. At municipal and county levels, effective application of the “Double Evaluation” requires that the three categories of development suitability assessment—ecological protection, agricultural production, and urban development—produce non-overlapping results. However, current methods, mainly based on the Main Functional Zoning Evaluation at the provincial scale, fail to produce strictly non-overlapping results at municipal and county levels.To address this limitation, this study introduces a novel approach leveraging trade-offs and cascades of ecosystem service capacity. Ecosystem Service Capacity is defined as a unified measure integrating three forms of resource and environmental carrying capacity: resource carrying capacity, environmental assimilation capacity, and ecosystem maintenance capacity. A Trade-off Correlation and Cascade Model (TCCM) is developed to assess resource and environmental carrying capacity by analyzing trade-offs and synergies among all pairs of the four dimensions of ecosystem service capacity—provisioning, supporting, regulating, and cultural. The synergistic interaction dimensions of ecosystem service capacity generate spatial clusters, identified as ecosystem service bundles, representing specific manifestations of resource and environmental carrying capacity. These bundles not only reflect resource and environmental carrying capacity but also guide land development suitability: areas with strong resource carrying capacity are best suited for agriculture; areas with high assimilation and maintenance capacity are prioritized for ecological protection; and lands lacking these capacities are designated for urban development.The method was applied in Youyang County, Chongqing. Results indicate that it effectively eliminates overlaps among ecological, agricultural, and urban suitability and elucidates the relationships and technical rationale underlying the two assessments—resource and environmental carrying capacity and development suitability. The findings highlight that: (1) the Main Functional Zoning Evaluation operates at the provincial scale but not at municipal or county levels, reinforcing the potential for overlaps among ecological protection, agricultural production, and urban development suitability assessments; (2) ecosystem services exhibiting synergistic relationships and spatial agglomeration formed distinct clusters, representing areas with high resource and environmental carrying capacity that correspond closely to lands suitable for ecological conservation and agricultural production; and (3) areas lacking sufficient resource and environmental carrying capacity correspond to lands suitable for urban and rural development.The “Double Evaluation” method developed in this study is simple, practical, and easy to apply. It provides an effective framework for delineating the “three zones and three red lines” in territorial spatial planning.