In order to solve the problems of too many attempts, slow splicing speed, low restoration accuracy and completeness in artificially restored paper-based cultural relics, an automatic splicing algorithm based on angle and edge length of fragments was proposed. Firstly, the fragment images were pre-processed and coarsely matched according to the angle value of the fragments, and the fragment images with the same angle value were found. Then, on the basis of coarse matching, thin matching was made by using the edge lengths of the angles of the fragments to reduce overlap, and the basic matching results of the fragment images were obtained. Finally, a concave-convex function was used to make up the fragment images of opposite direction, and a oscillating function was used to make up the gap of the final matching images to obtain complete splicing results. Theoretical analysis and splicing simulation experimental results show that compared with automatic splicing algorithms such as feature points, approximate polygon fitting and angle sequence matching, the splicing accuracy, splicing completion and splicing time of the proposed algorithm were improved by at least 12, 11 and 10 percentage points, respectively. The proposed algorithm based on angle and edge features reduces the cumbersome image calculation and accurately corrects the fragment matching result, which enables efficient and highly accurate matching of irregular fragments in actual relic restoration.