Long-length fractured vertical well has been applied widely, but there is still not productivity prediction model for longlength fractured vertical well in the low permeability oil reservoirs. In view of the fluid flow mechanism around the vertically fractured well, the productivity prediction model of long-length fractured vertical well with infinite conductivity and finite conductivity is derived by using conformal transformation and bilinear flow theory in consideration of starting pressure gradient. The IPR curve is draw to analyze the influences of hydraulic fractured parameters on long-length fractured vertical well productivity. Combined with the actual example, the accuracy of this prediction model is verified. The well productivity is influenced by the fracture length more deeply than the fracture conductivity, and there is an optimal fracture conductivity for long-length fractured vertical well under certain fracture length.