Abstract: The formation of a complex fracture network through hydraulic fracturing is a prerequisite for the efficient development of shale gas. The spatial distribution of bedding planes and natural fractures directly influences the propagation of hydraulic fractures and the complexity of corresponding networks. Combinations of the software COMSOL Multiphysics and MATLAB are used to establish a coupled seepage-stress-damage model, considering the heterogeneity of shale reservoirs. A grid coverage method based on the box counting method is introduced to determine the fractal dimension of its complex fracture network, evaluate the hydraulic fracturing effectiveness in numerical simulations, and reveal the complexity of the hydraulic fracture networks resulting from the interactions of bedding planes and natural fractures. It can be concluded from the numerical simulations and discussions that:(1)The bedding plane tensile strength and angle significantly influence the complexity of hydraulic fracture networks. This is evident as both lower and higher tensile strengths of bedding planes make it more difficult to form complex hydraulic fracture networks. In contrast, shale reservoirs with larger angle bedding planes are more prone to form complex hydraulic fracture networks. (2)Considering the lower tensile strength of natural fractures, the propagation path of hydraulic fractures is easily activated and changed, resulting in greater fractal dimensions and more complex fracture networks. In particular, natural fractures with larger angles are along with the maximum principal stress direction, the propagation path of hydraulic fractures is significantly changed, resulting in higher fractal dimensions and more complex fracture networks. (3)Moderate stress ratios are more likely to form complex fracture networks. A stress ratio of 1.5 has been analyzed to represent the highest fractal dimensions and the most complex hydraulic fracturing networks. These investigations can provide scientific support for the assessment of hydraulic fracturing effectiveness and optimization of fracturing techniques in shale reservoirs.