Abstract: The paper presents a method, or Semi-Analytical Element Method which marries the Finite line in the upper structure with the Special Boundary Element Technique in the soil. The equation of motion to this dynamic mathematical model in the frequency domain is first established. The paper designs the computer program and calculates the actual problem. Compared the calculated results of the program SSAP with those of it, this paper′s theory and computer program are proved to be right and practicable.