The influence of sodium salicylate (NaSal) concentration on the linear micelle formation in an aqueous solution of cetyltrimethylammonium bromide (CTAB) is investigated by the frequency-domain electric birefringence relaxation spectroscopy (FEB method). The contour length L of linear micelles is found to increase with increasing NaSal concentration. C-s but for further increase of C-s in excess of the CTAB concentration, L decreases, i.e., linear micelles break into shorter pieces. The FEB result indicates also that the diffusion constant of salicylate ions bound to a linear micelle is nearly independent of C-s with an average value smaller than that of free salicylate ions.