The Tangshan M_L5.2 earthquake in 2012 occurred against the background that earthquake with M ≥ 5.0 in the old earthquake zone was calm for 17 years,and its magnitude was significantly higher than that of the Tangshan earthquake sequence. In this paper,the TomoDD method was used to invert the seismic data from May 2010 to May 2016 in the Tangshan area at two-year intervals,and obtain the three-dimensional seismic P and S waves of the crust before and after the 2012 Tangshan M_L5.2 earthquake. Combining the precise positioning of the source parameters of the earthquake,this paper compared and analyzed the variation characteristics of the velocity of the subsurface medium in the source region before and after the earthquake. The study found that the epicenter was in the high-low-speed transition zone before the earthquake,the wave velocity near the epicenter after the earthquake has decreased to some extent.