The delineation of ecological conservation priority areas (ECPA) emphasizes cost-effectiveness in planning and management, optimizing resource allocation to maximize the stable supply of ecosystem services (ES). Mountain regions are crucial foundations for maintaining ecological security and represent areas of high ecological value. However, they exhibit prominent ecological vulnerability and sensitivity, necessitating strengthened ecological protection to address impacts from human activities and environmental changes. This study employs the Taihang Mountains in China as a case study to develop a hierarchical identification framework for ECPA based on ES and their trade-off and synergy relationships. The framework identifies ECPA from the perspectives of conservation scale and conservation objectives, based on systematic assessment and analysis of spatiotemporal patterns and change characteristics of ES and their interrelations. Our findings indicate that from 2000 to 2020, the ES in the Taihang Mountains underwent notable periodic changes, primarily exhibiting a declining trend. Water conservation (WC) increased by 2.93 × 10 m, while soil retention (SR) and carbon storage (CS) decreased by 2.85 × 10t and 1.10 × 10t, respectively. Habitat quality (HQ) declined by 0.03, and landscape aesthetics (LA) remained relatively stable with only a 0.01 increase. High-value areas for WC and SR services occupy a small proportion and are concentrated in the central region. In contrast, high-value areas for CS, HQ, and LA services were widely distributed, extending from north to south throughout the entire region. ES exhibited distinct gradient characteristics, with increasing elevation influencing these services' supply and fluctuation intensity. The trade-off and synergy relationships among ES remained stable and were predominantly characterized by significant synergistic relationships. High-high synergy areas exhibited strong spatial dependence, were concentrated in high-elevation regions, and showed an upward trend. The spatial coherence of ECPA from the perspectives of conservation objectives and scales was relatively high. As conservation objectives and scales expanded, marginal protection efficiency gradually decreased, though it remained above 1.5. Integrating conservation scales and objectives could cover an area of 19,571.33 km in the Taihang Mountains, ultimately achieving a minimum of 19.54 % for individual ES and 22.90 % for comprehensive ES. This study suggests that leveraging nature reserves can facilitate the practical implementation of ECPA, providing a framework for decision-making processes concerning ecological protection and ES management in mountainous regions.