Eco-linguistics is an interdisciplinary subject of ecology and linguistics. This paper aims to dig out the current situation and the corresponding countermeasures and reasonable proposals of Zhoushan fisherman's song as an endangered language in the perspective of Eco-linguistics. The analysis of register theory, including the field of discourse, the tenor of discourse and the mode of discourse of Zhoushan fisherman's song helps us to better understand man-sea relation, to provide a solid theoretical support for inheriting marine folk culture, to protect marine ecological environment, to achieve sustainable development of fishery economy and build Zhoushan into a powerful "Fisheries City".