This paper deals with the principle and method of the utilization of the digital technique to design the velocity model of stratigraphic elastic wave, recounts the algorithm of seismic ray tracing method and makes calculation by using its reflection and refraction wave time-distance curves to the digital model. With practical examples, the paper analyzed the correlation between the complex velocity structure and the seismic profile. The achievements made can guide the interpreter to design a stratigraphic model according to practical geological conditions and make calculation, and the result can be obtained very fast.