The computer aided rejoining is an advanced technology for the arrangement of the bones or tortoise shells with inscriptions. In this paper, we have studied the algorithms for contour extracting and tracking from these shell images and algorithms for extracting the feature vectors of the contour segments. We established a database for the oracle shell images, and developed a computer aided system based on the contour matching technology. After a being rejoined shell is selected, this system can automatically find a dynamic database for the possible target shells. Based on which, the experts can carry out the shell rejoining only by hand-computer interaction.