Abstract: The present paper provides a theoretical proof for that although the buckling load equation for the bidirection reinforced laminated plates under shear is an implicit equation,the laminated plates which gives the highest shear buckling load,just as the laminated plates under axial compression, must be symmetrical laminates.Based on the analysis of sensitivity,it is proved that the number of different ply angles in an optimum laminated plate under shear is no more than 3,including 0℃ and 90°.Furthermore,based on the analysis of the numerical examples,it is illustrated that optimization of laminated plates under shegr can be simplified to a single variable optimization.