Homography can be estimated from corresponding points, lines, or textures. But in some scenarios these features are not always available. As a supplement, the newly developed contour-based method is presented, which can be used to estimate the homography between any two planar contours of an image sequence. The proposed method improves the random sampling consensus (RANSAC) method into an iterative form. In the iterations, the random sample process of RANSAC is constrained by the previous iteration results. It reduces the blind sample process and ensures fast convergence speed. The experimental results demonstrate that the proposed method is effective.