In the process of oil and gas exploration, seismic data is one of the most important basic data. Seismic data are usually stored by the SEGY standard. With the development of 3D visualization technology in oilfield information, the Large Data Management (LDM) storage format was born to fit the needs of fast seismic line plucking and volume rendering. But the technical details of LDM format are not open. The paper, through customizing the LDM data, analyzing the storage position of each block data, analyses the storage format of LDM in detail, and gives the algorithm implementation, which combined with the basic principle of octree storage. This algorithm, under which the display module is extracted by the seismic profile, saves the storage space, and improves the efficiency of data extraction.