A sea-sky-line detection algorithm based on the improved active contour model is proposed to detect the elliptical sea-sky-line of the panoramic sea image. The visual saliency map of the image is obtained by the full resolution algorithm, and then the position of the panoramic device area in the panoramic image is extracted to eliminate its adverse effect of device area interference on the sea-sky-line detection. According to the characteristic that the panoramic sea-sky-line is elliptical, a shape energy constraint function is constructed and added to the active contour model, so a new energy function is formed. The new energy function limits the shape of the active contour in the convergence process, and the contour shape is converged to the panoramic sea-sky-line successfully. Experimental results show that this algorithm is applicable for panoramic images under different shooting conditions and its detection accuracy reaches 96%. The universality and robustness of the proposed algorithm are excellent.