Various methods have been proposed for interlocking adjacent caissons to enhance stability of harbor structures, i.e., breakwaters and quays. Among the methods, it was studied the method based on an open-cell caisson with rubble fills in an inter-cell formed by two facing opencells which consist of external walls and internal walls. Using ABAQUS, shear behaviors of an inter-cell were investigated under oblique wave loadings. Numerical results show that 60~70% of the shear load is transmitted to adjacent caisson through the internal walls, 30~40% is through the external wall. inter-cell formed by two facing opencells which consist of external walls and internal walls. Using ABAQUS, shear behaviors of an inter-cell were investigated under oblique wave loadings. Numerical results show that 60~70% of the shear load is transmitted to adjacent caisson through the internal walls, 30~40% is through the external wall.