Abstract: Fluid seepage process in horizontal wells production of tight oil reservoir shows obvious non-Darcy flow characteristics. Based on initiating pressure gradient and stress sensitivity, law of conservation of mass and pressure drop superimposition principle were used to infer the unsteady seepage flow pressure distribution equation for horizontal wells in tight sandstone reservoirs. The characterization of the seepage flow process of horizontal wells under different boundary conditions and the solution of relevant parameters can be obtained for this model by using mirror reflection theory, which is very practical. Meanwhile, the effect of initiating pressure gradient and stress sensitivity on fluid seepage in reservoirs was analyzed, which resulted in pressure distribution in horizontal wells under different initiating pressure gradient and permeability coefficient of deformation.