Abstract: Improvements on the effect of fracturing stimulation is essential for the economic and effective development of tight reservoirs, and it is necessary to consider the distribution characteristics of complex fracture networks while evaluating the effect of fracturing stimulation. Based on microseismic data, distribution characteristics of secondary fractures were obtained by using a fractal random fracture networks generation algorithm. By considering the physical properties variation of the near borehole region of fractured horizontal wells, a mathematical model of fluid flow in multi-zone porous media of fractured horizontal wells was established and then resolved. Based on the model, the influences of the complexity of secondary fractures on the flow were studied. The results demonstrate that the complexity of secondary fractures has a significant impact on the entire flow stage. The findings include the larger the fractal dimension, the higher the yield; the wider the stimulated zone, the longer the steady-state turbulence early linear flow and the bilinear flow will last. The fracturing stimulated area with the distributed secondary fractures is the main area in the early to middle stage of production, and it makes the largest contribution to the production. Thus, during actual production, the best approach is to increase the stimulated volume so as to improve the early production and to maximize the EOR of reservoirs. The research results can provide a theoretical basis ofr the evaluation of a volume fracturing effect of tight reservoirs and the optimization of fracturing design.