Aiming at managing the index directories in the NTFS file system, it uses B+ tree in some of books and magazines of NTFS, analyzes the 90H attribute, A0H attribute, B0H attribute in the folder recorder in the metafile $MFT and the structure of the index node in NTFS file system, observes to change the index directions in the NTFS by researching, deleting, inserting the file name in it by the mode of experiment. The experiment results indicate that the structure of the index directories in NTFS uses B-tree structure, but it isn't the standard B-tree structure.