Abstract: This invention relates to a method of data indexing on external storage devices by a specific index tree and it is applied in data bases, file systems, etc. It is based on B+-tree which is characterized by the fact that adjacent operations are recorded in addition to each branch of the internal nodes of the tree. After accumulating, these operations pour down in groups to lower nodes. The number of physical operations is minimized by the method when employing external storage devices and their life cycle is pro longed. The speed of indexing is enhanced many times without being substantially affected by the order of inputting the operations.