The throat of low permeability oil reservoir is narrow and small, the reservoir fluid flow resistance is big, and with the start-up pressure gradient, compare with medium and high permeability reservoir fluid flow, the characteristics are obviously different in performance for non-darcy flow at low speed. This kind of oil field reservoir started in the process of mining scope is small, the degree of use and the development effect is low. To solve these problems, this paper established considering start-up pressure gradient of the new unstable seepage flow mathematical model of non-darcy radial flow which the analytical solution and the productivity equation is deduced, established the effective radius of the use of low permeability reservoirs, and systemicly researched the calculation method of area well pattern of different types of non-darcy seepage.