Nowadays, competition among seaports in the world has become ever fierce. Most ports are attempting to gain more competitiveness advantages over others by increasing their productivity and enjoying economy of scale to larger extend. However, facts prove that the seaports’ common problem of underutilized capacity cannot be totally solved by these means. Proper marketing activities are urgently needed by seaports as well. On the other hand, social media as a brand-new marketing communication tool has already been intensively used by many other industries. In seaport industry, there seem also be some signs of the use of social media. But no existing research could offer us even primary understanding of seaport social media in aspect of marketing communication issues. In this thesis, we start to fill in this blank and offer some reference for further study. We firstly conduct a comprehensive literature review on relevant academic fields, such as marketing in general, service marketing, seaport marketing and social media marketing. Some existing achievements made by marketing practitioners have also concerned by us to complement our knowledge base. Afterwards, the marketing potential of seaport social media has been summarized. Then we take a look at the use pattern of social media among the top 100 ports in the world and the top 10 ports in Europe, North America and Asia respectively. Besides, both scoreboard and case study have been employed to evaluate the marketing usage of seaport social media quantitatively and qualitatively. To understand the ways of marketing communication on seaport social media in depth, we further generalize and analyze the communication on selected ports’ Facebook page in three facets, namely direction, content and image. In the end we conclude seaports have not fully realized the marketing potential of social media yet, even though the degree of understand seems not the same among different areas. Regarding our findings, we also offer seaport some suggestions on how to make more use of social media as a marketing communication tool.