Abstract: The nonlinear fracture extension in tight oil reservoir by hydraulic fracturing is characterized by statistic self-similarity, and the complex hydraulic fracture system can be described by the fractal bifurcate tree network theory. Based on fluid diffusion theory and pressure drop superposition principle, this paper uses semi?analytical method to estiblish the corresponding mathematic models for reservoir seepage and fracture seepage, and predicts the unstable productivity of a fracturing well through iterative algorithm, including influencing factors analysis of the productivity. The results show that the smaller the matrix permeability, the greater the contribution ratio of production rate from branch fractures, and the more favorable for generating complex fracture network. During the early production, the production rate from branch fractures is lower; up to quasi?steady state period, the production rate from branch fractures is increased rapidly, and the stable production stage is prolonged. The more complex the hydraulic fracture system, the larger the effective contact area of hydraulic fractures and the higher the production rate; also, the higher the branch fractures flow conductivity, the higher the production rate is. So, additional complex hydraulic fracture networks and incremental branch fractures flow conductivity are favorable for high and stable production of a fracturing well in tight oil reservoir