<p>Shale gas, an unconventional natural gas is primarily existed in shale formations and interlayers, requires hydraulic fracturing and other techniques to create an artificial fracture network to enhance reservoir permeability and facilitate gas extraction. Understanding the impact of discrete fracture network on hydraulic fracture extension is the key to the optimal design of shale gas accumulation fracturing. We used orthogonal tests to calibrate mesoscopic parameters and established a discrete fracture network model based on the improved fluid–solid coupling algorithm, taking the random distribution of the natural fracture location, inclination angle and length parameters into account, and investigating the effects of the in-situ stress state, the density of the discrete fracture network, and the injection rate on the hydraulic fracture extension under the discrete fracture network. The results show that: Compared with the traditional trial and error methods, orthogonal tests can calibrate mesoscopic parameters quickly and more purposefully with fewer tests; the discrete fracture network affects the extension direction of hydraulic fractures by changing the stress distribution; in the dense region of natural fractures, the increase in fluid injection rate can help to form a larger volume of hydraulic fracture network. The research results can provide theoretical and technical support for monitoring hydraulic fracture extension and optimizing construction parameters in tight reservoirs.</p>