We propose a new method of flow velocity estimation by analysis of time dependent beating signal using Spectral Optical Coherence Tomography. The oscillatory beating signal is caused by the Doppler shift of light reflected back from a mobile object measured in the interferometric set-up. This signal provides information about the velocity of the movable object. Measurements in model systems prove the method to give accurate results. Additional in vivo measurements of blood flow in the retinal vessels show potential applicability of this method in the field of biomedical imaging.