Abstract: Based on the calculation of the response coefficient Kw of the aquifer to the stress change, combined with the change of well water level, the stress field changes before and after the Tangshan Guye 5.1 earthquake were got by inversion, and the following conclusions were obtained: 1. In July, 2020, the stress field in Tangshan area had undergone an obvious turning change, from a compressive stress of 1.583 Pa to a tensile stress of −2.869 Pa, with a stress change range of 4.452 Pa. 2. The basic characteristics of the evolution of regional stress field are as follows: compression - strengthening - turning - tension - weakening - recovery From the perspective of spatial process: stress concentration - growth and expansion (west east mode) - breaking the control of active faults, post-earthquake turning - weakening transfer - recovery. Characteristics of strength evolution: the stress field around the focal area gradually increases from normal to a certain extent, and then slows down. After the earthquake, it weakens rapidly until it disappears. 3. The conclusions obtained by using the long-term variation trend of well water level, two-year variation of pore pressure of well water level, focal mechanism solution and GNSS solution are consistent with the stress state of regional stress field obtained by using the response ability of aquifer to stress change: on the whole, the stress state is nearly EW compression and nearly NS tension.