Considering the wavefront aberration and speckle noises in long distance digital holography, the wavefront correction based on image metric optimization and speckle noise reduction based on multi-image averaging are studied, in which the multi-images are generated with aperture dividing technique. A digital off-axis holography experimental setup is established, and the wavefront aberration correction experiments are performed, in which the gradient descent algorithm is used to optimize the image sharpness metric. Multi-images with different speckle noises are reconstructed by dividing aperture into certain small parts, and average operation is performed among those multi images. The results show that the image resolution is improved effectively while the aberration is corrected with image metric optimization method, and a higher quality image is obtained after multi-images averaging.