Carbonates play a crucial role in transporting surface carbon-bearing materials into the Earth's deep mantle through subduction. The recycling process of subducted carbonates is considered a pivotal process in the deep carbon cycle within subduction zones. During subduction, carbonates undergo decarbonation reactions to varying extents, releasing carbon-bearing fluids or melts into the mantle, thereby significantly impacting its composition and redox state. Today our comprehension of the carbonate recycling process in subduction zones largely stems from restricted investigations of (ultra) high-pressure metamorphic rocks, mantle xenoliths of different depths, experimental petrology and molecular dynamics conducted under conditions of high temperature and high pressure. A thorough understanding of the processes involved in subducting carbonate recycling is crucial for deciphering the geochemical and dynamic behavior of carbon in the deep Earth. This paper provides a comprehensive review of the subducting carbonate recycling process. It examines various decarbonization mechanisms, including metamorphic decarbonation, dissolution decarbonation, melting decarbonation, and redox decarbonation. By integrating these mechanisms with the thermal structure of global subduction zones, the paper investigates the distribution of carbon states and its migration patterns. Furthermore, it explores the impacts of these processes on the oxidation processes within both shallow and deep Earth environments.