With further progress of oilfields' development all over the world, more and more tight sandstone reservoirs are being put in production. The existence of low velocity non-Darcy flow has been proven, so in this paper the three-dimensional three-phase horizontal well numerical simulator was developed with considering the non-Darcy flow. The comprehensive comparison and analysis of the simulation results of Darcy flow and non-Darcy flow were provided including liquid production rate, oil production rate, water cut, reservoir pressure, oil saturation distribution and pressure distribution. With considering the non-Darcy flow, the fluid flow in reservoir consumes more driving energy, the water flooding efficiency was reduced.