In the early 1980’s, we used low velocity segments in average velocity fanned figure of seismic rays to judge the existence of geological anomalies and used the intersection method to locate their positions, but we couldn’t determine the shapes of anomalies, and if the low velocity segments in fan figure were not obvious, it is difficult to distinguish the anomalies reliably. Recently, with CT technology, we carried out some experiments in two different rock areas, one is in the granite area in Three Gorges dam site ; the other is in the limestone area in Goupitan dam site in the middle reach of Wujiang river, Guizhou Province. Compared with medical CT, geoCT is more complicated because there are more unknown factors and rapidly changed parameters, limited observation data and directions, and greater medium velocity change gradient (more than 5%). With the practice of engineering geo-CT, we have studied some useful methods of inversion and got some good results.