[Objectives] The damage stability of large cruise ships has always been the focus of attention in the industry, and solas2020 greatly improves the requirement of damage stability subdivision index R for passenger ships. This paper starts with the optimization design of the layout details, and deeply excavates the ideas and technologies to improve the damage stability subdivision index a, so as to achieve the minimum change of ship type and meet the requirements of SOLAS Convention on damaged stability of cruise ships. [Methods] In this paper, taking an large cruise ship as an example, through calculation, analysis and comparison of the influence of different detail design schemes on damage stability subdivision index A, the key design factors affecting subdivision index A are found. [Results] The ship can meet the design requirements of damage stability. [Conclusions] The results show that the subdivision index A of the cruise ship can be improved to a certain extent through the refined design and optimization layout, thus the optimization of the main dimensions of the cruise ship is limited to the minimum range.