Open-sea oil terminal’s berth length optimization is a complex multi-criteria decision making problem. Therefore, this paper proposes a multi-criteria fuzzy optimization model for open-sea oil terminal’s berth length. The model is to improve port operations and safety by considering line tensions and theirs nonuniformity coefficients, and vessel motions as criteria, and the best alternative can be identified easily by ranking the value of weighted relative optimal degree. Finally, its application of optimizing the berth length of a north open-sea oil terminal is also given, and the results show that the proposed model is easy to use, reliable and applicable in optimization of open-sea terminal’s layout.