Abstract: The shear buckling of steel Plate shear walls stiffened vertically by closed form stiffeners is investigated,and curves of relating shear buckling stresses to flexural and torsional rigidities of stiffeners are presented. Threshold rigidities of stiffeners determined by the demand that the critical shear stresses be equal to the buckling stress of simply supported sub-panels,are presented. In the case that the rigidities of stiffeners are less than the threshold value,a formula is proposed relating the buckling stress to the rigidities of stiffeners. Plates stiffened by one side channels or stiffened by one side channels alternately on the both sides of the plate are analyzed and compared with double-sided stiffeners. A modification factor is proposed for the threshold stiffness of one-sided stiffeners.