An efficient numerical simulation method has been developed to simulate the coupled processes of fluid flow and geomechanics in fractured shale oil reservoir by coupling the embedded discrete fracture model and extended finite element method. The innovation of the proposed method is that the effect of hydraulic fracture on seepage field and stress field can be accurately described by explicit dimensionality reduction. At the same time, the dynamic change process of hydraulic fracture aperture and the influence of fluid pressure in hydraulic fracture on fracture deformation can be simulated. When meshing, it is only necessary to perform orthogonal meshing on the bedrock system, regardless of the geometry of the fracture, and a set of meshes is selected for both the seepage field and the stress field, so that the complexity of meshing is greatly reduced. In the proposed method, the flow equations were solved by the mimetic finite difference method which can ensure the local mass conservation and deal with the full-tensor permeability, the geomechanics equations were solved by the extended finite element method which can be used to simulate the displacement discontinuity between the fracture surfaces. Lastly, several numerical examples have been performed to show the accuracy and applicability of the proposed method.