Grillage is common types of structures in marine and land-based structural system. Grillage system that increases the stiffness of plate used by two rectangular stiffeners is a part of deck, side shell and bottom of ships. The worst load point of those structures is dependent on the loads, which are vertical, in-plane or combination of those directions as well as boundary conditions. The worst deflection point is produced when the point load is examined at central intersection. But the worst loading point would not necessarily be at the central point. To find the worst load point, a moving point load is applied to along the vertical and horizontal beams around mid-spans. Direct stiffness method is used as an analysis tool. Structural model tests are also carried out to confirm the theoretical analysis results. To find the optimum arrangement of grid system under a given point load, an optimization technique is applied. In this case, the minimum weight is the objective function and allowable stress, deflection and other dimension limitations are constraints.