Ecological restoration projects (ERPs) play a crucial role in enhancing ecosystem services, but their impact remains unclear, particularly in fragile mountain ecosystems characterized by high heterogeneity and rapidly varying altitude. Using China’s Taihang Mountains as a case study, we quantified the spatial and temporal changes of water yield, soil conservation, carbon storage, plant diversity and multi ecosystem services index (MESI) from 2000 to 2020, revealed the relationship between ERPs and ecosystem services by correlation analysis and redundancy analysis. The results showed the following: (1) Over a 21-year period, the average values of these ecosystem services were 49.68 mm, 268.71 t/hm ², 108.91 Mg/hm ², 0.69, and 1.33, respectively. (2) The increase in ecosystem services due to ERPs varied significantly. For instance, soil conservation showed a growth rate over five times higher than the others, while water yield grew by only 8.1%, and the MESI increased by 15.33 %. (3) Forest land restoration was the most significant types of ERPs, contributing 152,500 hectares of afforestation and a 56.94% improvement in ecosystem services. (4) The dominant factors of ecosystem services varied in different altitude range, in low-elevation area, terrain was the dominate factor, whereas the impact of ERPs was more pronounced in middle-elevation regions. In high-elevation area, vegetation factor was the primary driver. This research provides a theoretical basis for mountain ecosystem management and ecological engineering strategies.