There are many hollow areas underground of Dongjiagou coal mine.Due to construction,the distributions of these areas are detected by seismic CT(Computed Tomography) technology.CT technology of elastic wave which adopts the basic principle of section X-ray scanning is a kind of new method of geophysical exploration.We can get the distribution information of physical parameters of rocks or soil underground by different responses of boundaries to elastic wave.Thirty-four hollow areas are delineated in the study area of Dongjiagou coal mine by CT detecting and some other information.From drilling testing,the exact ratio of location reaches 87.5%.