Using the equations and principles of the velocity tomography technology, the authors studied the forward and inversion method for the geological model. The results show that such parameters of the model as its shape, location and slowness can be accurately obtained. First of all, the forward model was set up, the field was divided into regular rectangle grids, and the transmitting and receiving devices were installed respectively on the left and right edges of the section. Within the continuous transmission and reception, each velocity radial time can be obtained on the model. Then 20% noise was added to the travel time, the model was rebuilt with the mature ART method, and the inversion was employed to the model. It is shown that the inversion result approximates to the forward model, and the calculation precision and velocity are satisfactory.