The invention discloses a triangulated irregular network (TIN) data storage format defining and data processing method based on a directory index structure. The method comprises the following steps: creating an index triangulated data link table and directory index data; traversing a point set, and terminating implementation of the method if the traversal is completed; if the traversal is not completed, judging whether a point P is in the index triangulated data link table or not, and if the point P is not in the index triangulated data link table, searching for a data position of the point P in the directory index data, loading the data position of the point P into a memory, adding the data position of the point P into the index triangulated data link table, and then re-judging whether the point P is in the index triangulated data link table or not; if the point P is in the index triangulated data link table, searching for a triangulated position of the point P in a manner that the point P serves as a node; and calculating altitude data of the point P, and traversing the point set for a second time. The method provided by the invention has the advantages that TIN data is created and stored, and data processing is carried out based on a storage structure, so that the time efficiency for altitude data analysis can be effectively improved, and the memory usage amount of a computer is reduced.