—Based on the micro-structure of the 3D full fivedirectional braided composites inner unit cell model and the dual-scale characteristics of braided preform porosity, this paper established a model for calculating the permeability of 3D full five-directional braided preforms. By applying periodic boundary condition, the axial and vertical filling processes of 3D full five-directional braided preforms are simulated using the two-phase model in Fluent, and the axial and vertical unsaturated permeability of the preforms with different braiding angles are obtained. The simulation results shows the regular pattern that how the permeability responds to the change of the braiding angle: the axial permeability of 3D full five-directional braided preform is larger than the vertical one, and with the increase of braiding angle the axial permeability increases while vertical one decreases. Furthermore, the permeability of preform is much larger than the permeability of fiber bundles, which leads that the macro speed of resin is much larger than the speed of infiltration. So the resin filling time should be extended to realize the completely infiltration of the fiber bundles.