Land-use change in peatland area usually related to large carbon dioxide (CO2) emissions owing chiefly to drainage, which lowers groundwater level (GWL), and potentially affects regional and global carbon balances. The dynamics of carbon dioxide emissions from peat soil consists of root respiration (autotrophic respiration), peat decomposition (heterotrophic respiration and litter decomposition), and emission from dissolved carbon in water. Recently, peat decomposition study, which is free from root respiration still limited, even this process is one main factor of carbon balance on peatland environment. This paper analyzed various data about peat decomposition from direct measurement using subsidence and closed chamber methods in Indonesia, at different land conversions, from primary forests to secondary forests and or agricultural and plantations. Generally, different land conversion produced different peat decomposition. Primary forest produced lower peat decomposition compare than that of secondary forest or plantation fields. Peat decomposition also affected by environmental conditions such as groundwater level, soil temperature, and plant species that grow on the land.