Abstract: One of the main influential factors on the survivability of a surface combatant is its vulnerability to weapon effects,which means that its damage stability determines the vulnerability of a vessel. Currently,a surface combatant's damage stability is mainly assessed via the deterministic method,which offers no comprehensive assessment compared with the probabilistic method. This paper discusses the probabilistic method of evaluating the damage stability of a surface combatant,presents a new method named'variable interval linear interpolation'for the calculation of survival probability,and develops numerical procedures. Taking a certain combatant as an example, through calculating the damage probability P_i and the survival probability S_i,the subdivision index A is obtained by the sum of the product of P_i and S_i for each compartment and compartment group. Research shows that,by taking the subdivision index as an evaluation index and considering the damage effects of different weapons and collisions,the probabilistic method can realize a quantitative overall assessment of a surface combatant's damage stability,thereby providing a way to increase the survivability of a combatant through the optimization of the hull subdivision in the primary stages of ship design.