The orientation of fibre direction in layers and number of layers of composites play a major role in determining the strength and stiffness. Thus the basic design problem is to determine the optimum stacking sequence of the composite laminate. Many methods are available at present for the design optimisation of structural systems. However, these methods are based on mathematical programming techniques involving gradient search and direct search. These methods assume the variables are continuous. In this paper a different search and optimisation algorithm, known as the Genetic algorithm of Goldberg [1], has been successfully applied to obtain optimal fibre orientation of multi-layer plates, which considers the angle of fibre orientation as a discrete variable. The principle of GA is applied to obtain optimal layers and the orientation of fibres for stiffened square plates for both the symmetrical and antisymmetrical orientation of fibres subjected to uniaxial, biaxial and shear loading. Plates composing two to nine layers were analysed for their critical buckling load.