To repair Thangka relic by digital technology, the damaged regions, which Thangka are segmented, must be solved firstly. The algorithm based on maximum entropy and local priority is proposed to segment damaged regions of rip Thangka, considering the extent of damaged features and color in contrast to neighboring regions. Firstly, the gray image of Thangka is segmeted using maximum entropy algorithm. The false damaged regions are removed and the seriously damaged regions are obtained. Secondly, the gray image of Thangka is segmeted by local priority algorithm, the false damaged regions are removed and the transition of the damaged regions are achieved. Finally, the serious damaged regions is combined with the transition of the damaged regions and the ultimate segmentation result is gained. Experimental results demonstrate that the proposed algorithm can not only segment damaged Thangka effectively, but also segment damaged murals etc, which shows the effectiveness and robustness of the proposed algorithm.