Abstract: A sandy-soil sample buried at nearly 600m depth in the Juye mine area of Shandong Province was tested under, triaxial unloading at 12MPa confining pressure on triaxial test machine and the microstructural change of the sandy-soil sample in the whole process was detected by CT equipment. The CT photographs are processed and analyzed with computer image analysis method. The essential characteristics of structural change of the deep buried sand soil sampling . The deformation and failure processes under the condition of high pressure unloading test are analyzed.