As a coherent digital holographic imaging method, the speckles noise degrades the image quality. To solve this problem, a method to reduce speckle noise is proposed for digital holography. A series of digital holograms is obtained by shifting object slightly. Each hologram is reconstructed individually, while the differences between these retrieved complex amplitudes due to the object shifting are corrected with phase compensation and image registration algorithms. So all reconstructed complex amplitudes of object have same distribution, but uncorrelated coherent noise patterns. The speckle noise is well suppressed by averaging these reconstructed images. The theory and experimental results prove that the method is effective and feasible.