Sandwich structures have low weight and high stiffness. Sandwich panels with open and prismatic cores are a kind of these structures that have special properties. These panels are named based on the number of corrugations (n) of the core. In this paper weight optimization of these panels is carried out by Gravitational Search Algorithm based on yielding and buckling constraints. This algorithm is a heuristic algorithm that is based upon the Newtonian gravity force and the laws of motion. For optimization of the weight, core and surface thickness and panel height are assumed as design variables. The results show that for a specific panel, the design variables and the weight of panel are increased by increasing the load. Also the core and surface thickness are decreased and the weight and panel height are increased by increasing core corrugate number at a specific loading. The panels with n=1 and n=2 have the minimum weight and highest structural efficiency. By comparing the results with some previous studies, it is shown that the Gravitational Search Algorithm is a useful tool in achieving lower weight in these panels and has a good convergence rate.