In this paper, we propose an efficient building identification algorithm to allow users to take a picture by mobile phones and get the building information in few seconds. First, we use the GPS and compass information to reduce the search area. Next, we use the concept of the flood fill algorithm to cutout the building parts in the picture. Then, by extracting SIFT features, we can calculate the similarities between the query pictures and pictures in the database. Finally, we rank the matched result and return the building information which is most similar to the input picture.