The pore structure of shale gas reservoirs is complex, with ultra-low permeability and natural fractures. Horizontal well fracturing is necessary for stimulation. During the fracturing process, hydraulic fractures will extend to open and connect with existing natural fractures while also experiencing deflection due to natural fractures and ground stress. This results in the formation of a complex network of seams. Existing productivity forecasting models do not consider these factors. Therefore, this paper derives a productivity prediction model that takes into account complex fracture morphology and multiple migration mechanisms, which is then verified through field case analysis to ensure its reliability. Based on this, the influence of fracture parameters related to main and secondary fractures on productivity is explored. The analysis of influencing factors shows that the conductivity of main and branch fractures has a great influence on the productivity; The larger the main fracture half-length is, the larger the main fracture conductivity is and the larger the gas production is. For the formation with uniform distribution of branch fractures, the higher the conductivity of branch fractures, the higher the density of branch fractures and the higher the gas production.