Forest ecosystems play an extremely vital role in the global carbon (C) storage. Mycorrhizal fungi are ubiquitous in forest ecosystems and have crucial effects on C cycling. Here we reviewed the functions of different types of mycorrhizal fungi driving the C cycle in different forest ecosystems. First, we briefly introduced the important functions of forest ecosystems and mycorrhizal fungi. We also summarized the results of recent studies on C cycling driven by mycorrhizal fungi in temperate and boreal forests, as well as tropical/subtropical forests. It is found that ectomycorrhizal (EcM) plants in temperate and boreal forests contributed less to aboveground biomass C but they were major contributor to belowground C stocks, indicating that the contribution of EcM vegetation to aboveground biomass C is relatively small, while underground C stocks positively correlated with the proportion of EcM plant biomass. However, arbuscular mycorrhizal (AM) fungi dominated in tropical and subtropical forests and had higher aboveground biomass in these ecosystems, indicating that the contribution of AM fungi associated with soil organic C and N pools may even exceed the contribution of soil microbial biomass. Besides, climate change factors such as atmospheric CO₂ enrichment, N deposition, land use change, warming, and drought were potentially important factors affecting the community structure of mycorrhizal fungi and the stability or decomposition of C in both temperate/boreal forests and tropical/subtropical forest biomes. Then, the mechanisms of mycorrhizal fungus-mediated C sink function in forests, and the mechanisms of different mycorrhizal tree species influencing the C cycle were emphasized in this review. In conclusion, the mycorrhizal fungi regulated C cycling function of the whole forest ecosystem by affecting the decomposition of litter, the formation of soil organic matter and the turnover of belowground root biomass. Specifically, EcM fungi had an advantage over free-living fungi in nutrient competition for the decomposition of difficult litter, and the Gargil effect occurred only in forests dominated by difficult organic matter, while AM fungi were unable to directly utilize organic nutrients in the soil, but preferred to utilize "inorganic" nutrients. In addition, mycorrhizal roles in forest C cycle largely depended on the mycorrhizal type of the (dominant) trees and mycorrhizal fungal community structure in forest soils, because mycorrhizal type of the trees had the direct or indirect effects on photosynthetic product allocation across host plants, as well as the number and function of extraradical mycelium and metabolic activity of soil microbes. We also proposed some perspectives in terms of establishing controlled field experimental platform, developing cutting-edge methods or techniques, and strengthening the research on the effects of global changes on mycorrhizal fungi and forest soil C sink function in future. This mini-review highlights the important C cycling function of mycorrhizal fungi which may provide key implications for promoting the soil climate mitigation in forest ecosystems.