The stress environment of shale oil reservoirs changes continuously with fracturing construction, which directly affects the expansion direction and range of fracture network, and then influences the design of later fracturing programme. Aiming at this problem, considering the non-homogeneity of shale reservoirs, the range of fracture extension during fracturing and geomechanical parameters, a simulation method for the dynamic evolution of multi-physics coupled stress field during fracturing of terrestrial-phase shale oil reservoirs was proposed, and a dynamic stress evolution model for the coupled seepage-geomechanics of the horizontal section of fracturing was established, combining the 3D static and 4D dynamic stress fields, and studying the influence of the fracturing modification behaviour on the geostress of well platforms in the horizontal section of the well. The effect of fracturing behaviour on the geostress and formation pressure in the well platform is studied in multi-dimensional and multi-scale. The study shows that: during the fracturing construction process, the changes of geostress are concentrated around the trajectories of the production wells, the fracturing fluid seeps into the formation through the seam network of the wellbore, the pressure in the wellbore is gradually transferred outward, the formation pressure in the near-wellbore area rises sharply, and the range of the pressure wave is constantly expanding; the direction of the geostress field of the horizontal section of the fracturing reformed area is deflected by the deformation of the formation and extrusion, and the effective stress field and the geostress show the tendency to be reduced to varying degrees. The effective stress field and the ground stress show different degrees of decreasing trend. This method can provide new ideas and references for the optimisation of fracturing in domestic onshore shale reservoirs.