Abstract: At present, the research on 3D permeability test is in the initial stage in China. Based on the self-developed 3D permeability tester for coal samples, we can simulate the three dimensional fluid flow through pores of coal samples under the triaxial stress. The experiments of stress sensitivity of the permeability of coal samples were conducted under triaxial stress. The study shows that the impact of horizontal maximum principle stress on percolation ability of coal samples is larger than horizontal minimum principle stress; the three dimensional permeability of coal samples is sensitive to the stress in different directions, the strong-to-weak sequence of sensitivity is:the vertical stress>horizontal maximum principle stress>horizontal minimum principle stress.