Abstract: A semi-three-dimensional plastic limit analysis method of the buried large diameter cylindrical breakwater in crossanisotropic soft rail is presented assuming conditions of rotational symmetry about the vertical axis. The failure mechanism assumed is that wedge(s) near the mudline and an arc slip surface at the base of the cylinder are formed when the cylinder structure overturns, rotating around a point which is on the synunetry axis of the cylinder. The method can allow for the different soil strengths in triaxial compression, extension and simple shear. This problem is also analyzed by plane strain FE and three dimensional FE, in which the soil employs a Hill yield criterion. All FE analyses are done through ABAQUS. The failure mechanism assumed and the plastic limit analysis predictions are validated by finite element analysis. The results indicate that the capacity of the structure, allowing for the soil's anisotropy, reduces considerably.