Shamir gave the (t,n)-Threshold Secret Sharing Scheme of cryptography based on Lagrange interpolation. In this paper, the authors introduce it into image sharing and give a new kind of algorithm for image sharing based on moving lines. The mathematical scheme of moving lines is presented in this paper. Hereby, when an image is shared, the authors consider more original images, compute with rational curves of high degree, compare the differences between Lagrange interpolation and moving lines on image sharing of many frames, and give the application fault of Lagrange interpolation with high degree in image sharing. Finally, some experimental results for image sharing based on moving lines are presented.