Fire compartmentation is one of the most important and complicated ship general design work, especially for the passenger ships, such as the cruise ship and Ropax with large number of rooms. The traditional design method, which is based on two-dimensional (2D) drawings and human subjective judgement, costs heavy workload and is likely to induce mistakes. A three-dimensional (3D) assisted fire compartmentation method for ship cabins has been proposed based on the secondary development of the 3D modelling software UG through the programming analysis of the specification requirement logics. This method embeds the relevant knowledge requirements of the fire protection rules. It fulfils the functions of customizing the categories of the ship cabins, automatically creating the common interface of adjacent cabins, and automatically setting the common interface’s fire protection level, which is highlighted in different colors, according to the regulations. It also counts the usage of different fire protection levels, which can lay the foundation for helping the designers to optimize the cabin arrangement based on the objective of reducing fire protection materials.