Abstract: Hydraulic fractures are distributed irregularly due to strong tectonic stress, large dip angle formation, highly developed bedding and natural fissures of shale gas reservoirs in northeastern margin of Sichuan basin. Based on finite?element and discrete?element combined method, the transverse isotropic constitutive relations are introduced to represent lamellar shale and a 3D complex fracture propagation model has been established. Then the model is used to analyze several important parameters which could influence the fractures after stimulation, such as in?site stress difference, fracturing fluid viscosity, injection rate and natural fracture, etc. The modeling result shows that the larger the difference between vertical stress and the minimum horizontal principle stress is, the easier the vertical fractures will occur. Under the condition of the low differential stress (5 MPa), increasing fracturing fluid viscosity and injection rate is more likely to decrease the limit of bedding to fracture propagation, increase vertical fractures and improve vertical stimulation effect. The more developed the natural fractures without advantageous strikes in shale, the more the shear fractures will be under strong tectonic stress differences