Grazing is a key method for utilizing grassland resources in the Inner Mongolia Autonomous Region, and establishing suitable grazing intensity is essential for improving the resilience of grassland ecosystems. However, the precise effects of varying grazing intensities on grassland ecosystems are not fully understood, particularly concerning the variability and sensitivity of vegetation community structures and soil properties, necessitating further detailed investigation. Thus, this research performed a meta-analysis, synthesizing 1006 data points from 66 published studies, to comprehensively evaluate the impacts of various grazing intensities on above-ground biomass (AGB), below-ground biomass (BGB), pH, soil total nitrogen (TN), and soil organic carbon (SOC) in grassland ecosystems. The analysis revealed the response characteristics of these factors under varying grazing intensities. Furthermore, the study developed a structural equation model (SEM) to investigate the interaction mechanisms between key ecological indicators and influencing factors within the Inner Mongolia ecosystem and utilized the long-term grazing duration and intensity (LGDI) to clarify the trend of grassland degradation. The findings indicated: (1) Grazing substantially decreased AGB and SOC by 47.5% and 12.1%, respectively, relative to ungrazed grasslands. Light grazing had no significant impact, while moderate and heavy grazing reduced AGB by 45.7% and 81.6%, respectively, and heavy grazing reduced SOC by 19%. (2) The effects of grazing on grassland ecosystems varied by grassland type, with meadow steppes being the most affected, followed by typical steppes and desert steppes. (3) SEM analysis revealed that grazing intensity exerted a significant negative influence on biomass and soil properties, with impact coefficients of -0.487 and -0.193, respectively. Mean annual precipitation had impact coefficients of -0.464 on grassland type and -0.803 on soil properties, while mean annual temperature had impact coefficients of 0.404 on grassland type and -0.407 on soil properties. (4) Further analysis of the combined effects of grazing intensity and duration on grassland ecosystems showed that when the cumulative grazing intensity index reached around 4, the grassland ecosystem’s evolutionary trend shifted. This result suggests that after 16-20 years of low-intensity grazing, 8-10 years of moderate-intensity grazing, or 4-5 years of high-intensity grazing, grassland ecosystems may shift from factor-level degradation to type-level degradation, indicating a critical period for ecological protection and restoration. By quantitatively analyzing grazing intensity and its cumulative effects, this study clarifies the response characteristics and degradation thresholds of grassland ecosystems under varying intensities. The findings provide a scientific basis for identifying critical points of grassland degradation, revealing degradation pathways, and formulating grassland protection and restoration measures.