A fast Fourier transform method is mainly used in the digital holographic wavefront reconstruction of lensless Fourier transform, but the reconstructed image will not fully lie in the reconstructed area. Based on the recent image plane filtering technique, a method used for enlarge reconstructing object local area wavefield is proposed and the method allows the reconstructed image fully lie in the reconstructed area. Moreover, a digital holographic wavefront reconstruction example of object with fine structure is also given. Additionally, regard the digital holographic wavefield reconstruction as a coherent imaging process of an optical system which has a square exit pupil, we can derive the relationship between the resolution of object enlarged image and the optical system parameters. Finally, experimental results confirm the suitability of the proposed method.