Image mosaic aims to accomplish a complete image with stitching multiple images which overlap with useful image features.The paper introduces an improved algorithmwhich isto overcome the drawbacks of longtimecostingin feature point matching and high rate of wrong matching pointsbase on SIFT algorithm. In order to improve search efficiency when matching image features,the paper uses BBF (BestBinFirst) search algorithm instead of KDtreealgorithm,because BBF matching method is carried out according to the priorities of SIFT features, which is established based on the significance of subfeature within SIFT; While KDtree matching algorithm is based on space position from nearness to farness. Furthermore, this paper applies modified RANSAC algorithm to purify wrong matched SIFT features by calculating their error probabilities; while the traditional way adopts a threshold to filter out these wrong matched feature points.Comparing test results with the original algorithm in terms of image mosaicking quality on simple texture images and complex texture images, the test results show that the proposed method can improve the accuracy and speed of image stitching.