Abstract: The seismic wave CT results have the advantages of intuitive and reliable images, rich information and strong applicability. Practical results show that the seismic wave CT technology has a good detection effect in engineering geological survey, non-destructive testing of buildings, dam safety testing, and quality inspection of cutoff walls. The SIRT algorithm is a relatively mature algorithm of seismic wave CT theory. This paper presents a Matlab computer program for the FDM algorithm based on the idea of Vidale solution, Fermat's principle, Huygens' principle, and finite element analysis of the bending wave front hypothesis. This algorithm program overcomes the shortcomings of the SIRT algorithm and can be successfully processed Arbitrarily changing speeds, high-speed comparisons, sharp boundaries, and arbitrary measurement layouts are given to practice a few numerical simulation examples, combine the two together, compare before and after, draw conclusions, and guide engineering practice.