This paper addresses an improved cross-section analysis approach for calculating the deformation modes of thin-walled cross-sections with circular rounded corners in the framework of generalized beam theory (GBT). In the cross-section discretization, in contrast to the classic GBT one, the circular rounded corners are treated as independent circular walls, and deflection functions of the corresponding circular arches, which play the role of basis functions, are used to approximate the in-plane displacements of any points on the corner mid-line. Because the geometries of the circular corners are accurately modelled by curved elements, the proposed procedure is more efficient than those based on the polygonal approximation of the corner mid-lines. Illustrative cases concerning the employment of the procedure to four cold-formed cross-sections are presented to show its validity and potential. Through comparisons of the proposed procedure against that based on the polygonal approximation, it is shown that it yields accurate results with much coarser cross-section discretization.