The use of foam sandwich in wing structure can reduce the weight of structure. So the optimization of foam sandwich composite is important. An optimization algorithm is design to optimize angle of ply and thickness of plies simultaneously based on genetic algorithm. In the article the region division technique and the floating-point coded are taken in the previous optimization design. The optimization of the ply design of the foam sandwich skin of the composite wing structure is accomplished through the previous optimization method. The optimal result is that the weight is reduced by 38.2%.The result shows that the weight will be reduced by the optimal method. There are certain values for making use of foam sandwich structural.