Deep carbon recycling is an essential part of the global carbon cycle.The carbonates at the bottom of the ocean are brought to the mantle by subduction.Subsequently, deep carbon is released to the atmosphere in the form of CO2 through volcanism.At present, research on deep carbon recycling is still at its early stage.The proportion of subduction-related carbon and primary mantle-derived carbon in CO2 released by volcano is an important issue.Carbon isotopes can easily distinguish organic carbon from inorganic carbon.However, ～95% of subduction-related and primary mantle-derived carbon released by volcano is inorganic, which carbon isotopes find difficult to distinguish.Recently, Ca and Mg isotope geochemistry has provided important tools for tracing crust-derived material recycling.Here we focus on this topic by introducing the principles of C, Ca, and Mg isotopes in tracing deep carbon recycling and previous research results.We also summarize the research progress on the total storage and phases of deep carbon, CO2 fluxes which depend on the release via volcanism, the partial melting of the carbon-bearing mantle, and carbon behaviour during oceanic subduction. Deep carbon recycling is an essential part of the global carbon cycle. The carbonates at the bottom of the ocean are brought to the mantle by subduction. Subsequently, deep carbon is released to the atmosphere in the form of CO2 through volcanism. At present, research on deep carbon recycling is still at its early stage. The proportion of subduction-related carbon and primary mantle-derived carbon in CO2 released by volcano is an important issue. Carbon isotopes can easily distinguish organic carbon from inorganic carbon. of subduction-related and primary mantle-derived carbon released by volcano is inorganic, which carbon isotopes find difficult to distinguish. Recently, Ca and Mg isotope geochemistry has provided important tools for tracing crust-derived material recycling. Here we focus on this topic by introducing the principles of C, Ca, and Mg isotopes in tracing deep carbon recycling and previous research results.We also summarize the research progress on the total stora ge and phases of deep carbon, CO2 fluxes which depend on the release via volcanism, the partial melting of the carbon-bearing mantle, and carbon behavior during oceanic subduction.