Abstract: To reduce the difficulties caused by the processing of complex incident wavefields, which are usually encountered in earthquake engineering research, the approximate equivalence scheme is proposed in this paper. First, the incident site waves’ information in near-source sites from the source P wave is obtained by the spatial evolution method. And these incident site waves are classified into different types based on the wave spatial path. Then the angle accumulation characteristic of incident site waves is investigated. Finally, the approximate equivalent scheme which transposes masses of incident site waves into several equivalent waves is put forward. And the 4-angle approximate equivalent scheme and the 2-angle one are illustrated. The result shows that the number of incident site waves can be reduced respectively to 4 and 2, and the maximum errors of motions are respectively 1.14% and 2.78%.