Aiming at the optimization of speed and of final matching pairs for image mosaicing, this paper proposes an image mosaicing algorithm based on BRISK (Binary Robust Invariant Scalable Keypoints) keypoint detection algorithm and improved RANSAC (Random sample consensus) algorithm. The improved RANSAC algorithm aims to find more matching pairs through loops. The specific improvements are adding loops while calculating the number of inliers and changing the Euclidean distance used for inliers judgment to area. The experimental results show that the improved RANSAC algorithm increases the number of inliers, and the average back-projection error rate is reduced by about 10% compared with the original algorithm. Compared with the common mosaicking methods, the time cost of the mosaicking method proposed in this paper is reduced by about 50%. The method proposed in this paper can realize real-time and accurate image mosaic.