Abstract:This paper describes some esscntials of 3-D ray-tracing modeling technique, which are the 3-D mathematical model of seismic reflectors, the computaton of ray path the synthesis of zero-offset time section, and so on, Some factors, such as diffraction, reverse reflection branch, single source, multiple sources, constant velocity, varying velocity etc, are taken into consideration in the calculation of model, The FWJQ method for fractured reflector fitting and the ray projcction method for seeming the intersecting paints are feasible, The fine feasibility of 3-D ray-tracing modeling technique has been proved by Frenchmodel.In the 3-D modeling of the geology of GN prospect in Jianghan all field, a good correlation is obtained between the modified Q(base-ment), EL:, T:reflectors and the corresponding reflectors of horizontal stacking sections; and the reflection band of Ts reflector on synthetic seismic section is quite reasonable except fracture positions, In summary, this trial 3-D modeling technique leads to a new idea in analysing 3-D velocity, it is also significant to the research on applied 3-D modeling.