Based on the generalized Darcy’s law, considering the effect of start-up pressure gradient, the permeability anisotropy of low permeability oil-water two phase seepage model is established herein. Based on the principle of virtual displacement, a finite element program is developed. Taking the Daqing Su301 fault block, a rectangular five-spot linear injection-production well pattern as an example, we analyze the effects of start-up pressure gradient on low permeability reservoir micro-seepage and macro development dynamic trends. The research shows that, influenced by start-up pressure gradient effect, the low permeability reservoir seepage has a significant delayed effect, seepage velocity shows a“ladder shape”changing trend; the smaller the start-up pressure gradient, the higher of the initial oil production, but later the water cut rises up increasingly fast, leading to a much more obvious reduction of daily production; the greater the start-up pressure gradient, the lower the reservoir recovery degree, and along with the producing continues, it has greater influence on reservoir recovery degree.