mercury injection measurement is an effective petrophysical method to study pore structure of reservoir. Information about pore structure of porous materials can be obtained from capillary pressure curves. Based on the capillary—pressure data, this article studied the Pore structure characteristics and its effect of on permeability of Triassic Chang 7 reservoir in the southwestern Ordos basin. In order to understand the characteristics of pore structure, the mercury injection curves, pore throat distribution and the fractal of pore structure were studied. Moreover, we studied the influence of pore throat parameters on permeability by stepwise regression. The results reveal that the radius which makes the greatest contributions to the permeability is the most important factor affecting permeability. Sorting, sorting coefficient, mean size and skewness also have significantly effect on reservoir permeability. Besides, the radius which makes the greatest contributions to the permeability is close to but a little coarser than the radius corresponding the apex of hyperbola. At last, we discussed the influence of pore throat parameters sorted by stepwise regression on permeability. Meanwhile, other factors that might have impact on permeability were also constructively discussed.