There is pressure sensitive effect in ultra⁃low permeability reservoirs. It is of great significance for the development of oil fields to study the variation of matrix permeability with pore fluid pressure. Through the core simulation experiment in Chaoyanggou area with changing the fluid pressure to change net pressure, which reflects the real situation of the formation, the curve of the permeability with the change of net pressure is obtained, and the model of the relationship between net pressure and permeability is regressed. The results of the study show that the permeability varies significantly with net pressure, and the percentage of permeability change is about 20% in the stage of decreasing fluid pressure. The permeability does not change significantly with net pressure, and the percentage of permeability change is about 5% in the stage of increasing fluid pressure. At the stage of increase or decrease of fluid pressure, subsection fitting is adopted, and the change rule of permeability with net pressure basically accords with binomial relation with the correlation coefficient more than 0.99.