In this paper, the vibration of annular disks with linearly varying cross-section is analyzed by means of Bessel’s functions and an equivalent electro-mechanical circuit. By solving the equations of the equivalent electrical circuit, the natural frequencies and magnification factors are obtained for torsional and radial vibrations of annular disks. Then, the effects of variations of geometrical parameters such as inner and outer radii on the natural frequencies are studied. It is shown that the natural frequencies are more sensitive to the disk outer radius. For a disk with a constant inner radius, the torsional and radial frequencies are reduced as the outer radius increases. For verification of the proposed procedure, the FEM method is employed to check the accuracy of the results. There is good agreement between the FEM results and the results of this study. The present method is applicable for frequency analysis of disks with different cross-section variations.