Abstract: Objectives China Classification Society (CCS) has issued the “Guidelines for Assessment of the Second Generation of Intact Stability of Ships”, which established the assessment methods and technical requirements for typical dynamic stability failure accidents. Prediction of dynamics stability of ships under complex sea state is a major scientific issue in the field of safe navigation. Stability discrimination methods based on deterministic waves cannot accurately identify the instability domain in random waves. Methods In this paper, the stability characteristics of nonlinear roll motion in random waves are investigated based on stochastic analysis method. Based on the first passage theory, the first passage probability of the stochastic roll motion is calculated with given boundary conditions and initial conditions. Results The entire sea areas are divided into three parts, including high stability, medium stability, and low stability regions. Based on the first passage probability approach, the probabilities of the roll response exceeding 25° are calculated for full wave directions. Conclusions More information for stochastic stability of roll motion under different wave directions can be provided.