The rate and factors determining changes in the soil carbon pool after afforestation are still poorly understood, especially in arid and semiarid areas. This paper provides a review of the influence effect of afforestation on soil organic carbon (SOC) stocks based on a meta-analysis of 37 publications (including a total of 116 observations in the past 10 years), with the aim of exploring the major factors that can affect changes in soil carbon stocks after afforestation in arid and semiarid areas. This meta-analysis, which was based on a mixed linear model, indicates that the main factors that contribute to SOC accumulation after afforestation are previous land use, plantation age, mean annual precipitation, and mean annual temperature. It suggests that bare areas are the most suitable areas for afforestation, and that regions with precipitation of 250-400 mm and mean annual temperatures of 7.5-15ºC have a greater impact on an area’s capacity to accumulate SOC following afforestation. It shows that more SOC can be accumulated with the increase of plantation age. However, it also shows that plant species significantly affect SOC accumulation. This research will contribute to the development of policies of environment management and the models concerned with quantifying amounts of soil carbon sequestered by afforestation in these areas.