Naturally occurred radiocarbon (¹⁴C), as a powerful tool, has been used for decades for archeological and geological dating. Recent development and applications of Accelerator Mass Spectrometry (AMS) have made it possible to detect ¹⁴C  at its natural abundance in very limited sample sizes (<mg C). This has greatly increased the range of applications using ¹⁴C in natural science, particularly in the Earth sciences. In this paper, we briefly reviewed the principal and some recent applications of using natural ¹⁴C  in marine geochemical studies mainly in three areas:①¹⁴C studies of carbon cycling in the ocean; ②Using ¹⁴C as a tracer to determine the sources, transformation and turn over of the major organic compound classes in different organic carbon pools in the ocean; and ③¹⁴C studies of compound-specific biomarkers in marine sediments.  These studies have shown novel results and demonstrated that natural radiocarbon measurements at compound level provide a new and sensitive tool for determining the sources, transformation and biogeochemical processes of carbon cycle in  oceans in the past and at present both at large and small scales.