In order to evaluate the influence of the aeolian vibration on catenaries in operation and calculate their amplitudes under different wind speeds, a formula of catenary aeolian vibration in the vertical direction was deduced based on the modal analysis method. By solving the vibration dynamic equations, the natural frequencies and vibration modes of the catenary were obtained first. Then the exciting force acting on the catenary was deduced. Finally, the aeolian vibration amplitudes of catenary with respect to each frequency under different wind speeds were calculated, and the relationship among the wind speed, frequency, and amplitude was analyzed. The results show that the maximum aeolian vibration amplitude of the catenary was less than 1 mm in general, and the aeolian vibration similar to that of transmission lines would not occur. In a numerical example, the maximal amplitude of the catenary occurs at the wind speed of 1.44 m/s, and only reaches 0.96 mm. Therefore, the aeolian vibration would not influence the operation of the electrified railway significantly.