Abstract: This article adopted equivalent filtrational resistance method and bottom water driving vertical critical speed to derive the calculation model of critical production pressure difference and the calculation method of critical production capacity in bottom water reservoir exploitation based on the mechanism of bottom water coning of horizontal wells in bottom - water reservoir. The author analyzed how these parameters as vertical permeability, oil and water density, horizontal well position, oil and water viscosity and bottom water coning height affect critical production pressure difference and its result will be of great significance to confirm reasonable production pressure for horizontal well bottom water reservoir exploitation and provided reference frame to production capacity design.