One of the best ways to evaluate the safety of structures in highly uncertain and complicated ocean environment is to use the ultimate strength analysis and the system reliability analysis. Generally, the ship hulls are made of stiffened plates. In this study, a typical box girder with various stiffeners is employed as ship-type model for system reliability analysis. In this research Butte element method and the Best order second-moment reliability method ate applied to evaluate the system reliability of ship structures. First, a ship-type box girder is selected as an example to evaluate time system reliability. Parallel system of plates and stiffeners with associated plates are considered Finally, the failure probability on the midship section of a bulk carrier is evaluated by using thin system reliability method. It is believed that the global probability of failure of a ship can be obtained by utilizing the above system reliability analysis method.