The seismogenic structure of the Tangshan earthquake is the Tangshan rhombo-block, the maximum shear stress accumulated on its diagonal line under the action of NEE regional stress field, which is consitent with the Tangshan fault zone, so it became the initial beginning point of large fracture of the Tangshan earthquake. The evolution process of the precursors of the Tangshan earthquake showed two obvious characteristics: in space, they showed a transfer process from epicenter to outlying area to epicenter plus outlying area; in time, showing obvious stages, each speedup of the frequency of precursory anomalies all occurred after accurence of a strong earthquake in outlying area. In this paper, the earthquake-increasing and earthquake-decreasing theory is used to infer the strengthening action to the development of the Tangshan earthquake by occurrence of strong earthquakes in outlying areas. In a large area, the earthquake-increasing and earthquake decreasing effect of strong earthquakes can form many high stress concentrated areas. Most of these high stress concentrated areas are the occurrence areas of the coming strong earthquakes.