Abstract: The dynamic stiffness or frequency response characteristics of railway tracks are an important dynamic performance index for safe and stable commissioning of trains. The tracks are supported by discrete periodic sleepers which provide support stiffness and damping for tracks. However, actual periodic support detuning is unavoidable, causing the frequency response characteristics or dynamic performance of railway tracks degenerate. Therefore, the frequency response characteristics of tracks with detuning periodic supports and the relationship between them need to be studied. In this paper, the vertical dynamic characteristics of a long track beam with detuning periodic supports were considered. The partial differential equation of motion of the beam with discrete support stiffness and damping was established, and transformed to ordinary differential equation for the frequency response function. The frequency response function expression was obtained by solving the equation using the Galerkin method, which was suitable for non-periodic and periodic support cases. The frequency response characteristics of the beam with detuning periodic support stiffness and damping and the beam with detuning periodic support positions were calculated. The influence of detuning periodic supports was evaluated by comparing the frequency responses of the quasi-periodic-support and periodic-support beams. Numerical results illustrated that the periodic support detuning had high effects on the first resonance peak around the support and generated new frequency response peaks, and the random support positions had certain effects on the phase of high frequency response. The relationship between the frequency response characteristics and periodic support detuning was instrumental for the periodic support damage identification of tracks through frequency response.