As a long-term carbon sink, marine sediments preserve abundant organic carbon, and have important implications for climate change and carbon cycle. The organic carbon in the marine sediments would experience both aerobic and anaerobic degradation in the sediments. The process of the degradation is complicated, influenced by the chemical structure of the organic compound, the redox condition, the absorption of the sediments, temperature, pressure and biological activities. Therefore, it is essential to evaluate the effect of degradation in assessing the change in sedimentary organic carbons. The effect of degradation on sedimentary organic carbons can be estimated by degradation models. In this paper, the factors affecting the degradation process and the development of the models are reviewed, and the problems in model study are discussed.