In order to remove the thick cloud of aerial images, an improved image restoration algorithm based on improved Criminisi algorithm is proposed. The optimal inpainted block is selected by improving the priority function, and the searching strategy of the best matching block is optimized. In this way, the structural propagation error and cumulative error are reduced, and the matching accuracy is improved. Then the suitable size of the sample block is selected according to the local variance of the brightness of the pixels. A new confidence updating function is defined. The thick cloud area mask can be obtained through gradually refined cloud detection method and morphological closed operation. The experimental results of simulated data and real data show that compared with the traditional Criminisi algorithm, the completion effect of proposed method is more natural, and the thick cloud area in aerial images can be better repaired.