Abstract: During 1968 to 1970, the State Seismological Bureau, cooperating with the ministry of the petroleum industry had done a cross profile of seismic sounding from Yuanshi in Hebei province to Jinan in Shandong province, which is about 270kin long. This data was analyzed and interpreted by prof. Teng Jin wen in 1974. Reanalyzing this data in this paper, we first compare and trace the seismic phases of the reflection wave this area again, then make a inhomogeneous correction to the sedimentary layer near the ground surface, according to the cross section of SJ79-366 made by the ministry of the petroleum industry on the base of the one-dimensional model, we do the ray tracing and trave time fitting by using advanced two-dimensional inversion program and get an precise velocity-depth structure. Finally, we futher discuss the deep conditions with which strong earthquakes occur. 1) Crustal stress Institute, State Seismological Bureau 2) Geological Institute, State Seismological Bureau.