Theoretical analysis is presented to calculate the buckling shear flow of corrugated plates with Quasi-sinusoidal corrugations. The analysis is based on the Orthotropic Plate Theory which considers the corrugated plate as a flat plate having two different flexural rigidities in the two perpendicular directions. The Orthotropic Plate Theory although under-estimates the buckling loads (see Refs. 3 and 4) yet it is the usual approach to the shear buckling analysis of corrugated plates, thereby yielding the lower bounds on the buckling loads.