Abstract: On July 12, 2020, an M_S5.1 earthquake occurred in Tangshan, Hebei Province. The epicenter was located in the old earthquake area of Tangshan, and it was the largest earthquake in Tangshan region since 1995. The M_L≥2.5 earthquake recorded by Hebei Seismic Network from January 1, 2016 to December 24, 2020 in Tangshan area of Hebei Province was selected. The apparent stress value of the corresponding earthquake in the focal area was calculated by using the Brune model, and the stress adjustment process in the focal area was analyzed. Focal mechanism solution of Tangshan M_S 5.1 earthquake is calculated by CAP and GPat methods, and the seismogenic structure is analyzed in combination with the geological structure near the focal area. The results show that:（1）the variation process of apparent stress before and after the earthquake is as follows: the trend increases before the main earthquake, the peak value during the earthquake, and the trend decreases after the earthquake. （2）The main seismogenic fault is Tangshan-Guye fault, and the dislocation mode is right-lateral strike-slip type.