In this paper, an Equivalent Step-Index-Fiber Method(ESFM)has been extended to multicladding fibers. Upon defining the refractive index profile for the multicladding preform, the equivalent normalized index difference for the equivalent step-index-fiber of the preform can be exactly derived by the method so that varieties of transmission parameters for the fiber drawn from the preform would be predicted conveniently. Meanwhile, cutoff wavelengths of double-cladding elliptical fibers have been calculated as an example for part confirmation. Comparision between the theory and resuls form the experiment fibers, except individual cases, shows an accuracy of 5% in predicted cutoff wavelengths. As a result, for finally determining cutoff wavelengths or fiber-drawing radii of multicladding fibers, “trial and error” between fiber-drawing and cutoff-wavelength measuring procedures can be avoided in engineering practice, saving time, energy and material.