Processing method of laser speckle imaging is introduced into optical coherence tomography (OCT). Spectra varying with time are acquired at the same position. The spectra at each moment are transformed into OCT structure by the Fourier transform along the direction of wave vector. The OCT structure information at the same position and different moments is solved, and is then computed along the dimension of time by the Fourier transform to obtain the frequency spectrum of speckle. Imaging parameter is defined as the ratio of dynamic speckle to static counterpart in the frequency spectrum. The phantom experiment demonstrates feasibility of the method. The method is also applied to extracting blood vessel of a mouse ear, and the three-dimensional vascular structure is obtained.