The Arctic carbon sink was always ignored in the global carbon budget or dealt with in a simple way because the central Arctic was covered by ice yearlong. This view has changed, however, recently. With the increasing rates of global changes, the Arctic Ocean also changes. It becomes clearer that it is of paramount importance to understand the interplay between the carbon cycle in Arctic Ocean. This paper summarizes the current results on Arctic carbon sink (ACS), analyzes sources, variations and the controlling factors of the ACS, and then estimates the current status of ASC. The trend of ACS variation in the future is also evaluated here.