Delving into the impacts of reduced chemical fertilizers (RCF) and organic fertilizer substitution (OFS) on soil organic carbon (SOC) is crucial for understanding the response processes of agricultural SOC pools to fertilization and achieving sustainable agricultural development early. This study aims to explore the impacts of RCF and OFS on SOC under different climatic conditions, initial soil properties, and land use patterns. Furthermore, it endeavors to estimate the key influencing factors and clarify the natural and anthropogenic conditions conducive to SOC accumulation.【Method】After collecting and sorting out 142 published literature, we analyzed the variation characteristics of SOC content under RCF and OFS using meta-analysis. Thereafter, the influence degrees of various factors on SOC were systematically investigated by the Random Forest Model.【Result】The results revealed that SOC decreased by 2.61% on average under RCF. Notably, greater SOC losses were observed in temperate regions (with annual mean temperature < 10°C and annual mean precipitation < 1000 mm), whereas SOC losses were not significant with changes in altitude. Soils with high initial SOC content favored SOC retention. With soil’s initial pH and available phosphorus content increasing, the overall loss of SOC tended to intensify, with the highest SOC reduction reaching 6.91%, however, the effect of initial available potassium was the opposite. The declines in SOC under RCF were similar in farmland and orchards, while changes in SOC in vegetable fields were not significant. In contrast, SOC significantly increased by 14.39% under OFS, with subtropical regions at low to medium altitudes and annual precipitation < 600 mm being more conducive to SOC accumulation. Except for low levels of initially available nitrogen (50 mg·kg-1), no significant differences in SOC were observed among soils with different initial SOC, total nitrogen, and available nitrogen contents. With initial pH and available phosphorus content increasing, the cumulative effect of SOC enhanced, whereas the effect of initially available potassium was the opposite. Among different land use types under OFS, paddy-upland rotation and vegetable field utilization were most favorable for SOC accumulation.【Conclusion】Under the two fertilization systems, the climatic and environmental conditions in subtropical regions are more conducive to SOC sequestration. Compared to the subsurface soil, the impact of RCF and OFS on SOC in the surface soil was more significant. The decline in SOC of RCF was similar in both farmland and orchards, while the change of SOC in vegetable fields was not significant. In contrast, paddy-upland rotation and vegetable fields were the most favorable practices for SOC accumulation under OFS. Additionally, pH and initially available nitrogen were the most critical factors influencing the changes in SOC with RCF and OFS, respectively. These research results are of great significance for achieving carbon neutrality and sustainable development in agriculture as soon as possible.