X-ray computed tomography (XCT) reconstruction technique, finite element method (FEM)and pore scale modelling (PSM) were employed to investigate the displacement distribution of vanadium redox flow battery (VRFB) carbon felt and its effects on the transport properties under compression at pore scale. With contact friction, and extrusion bending between carbon fibers taken into consideration, the microstructure of a carbon felt was reconstructed by XCT first, then the 3D (X, Y and Z direction) displacement distribution of the microstructure with different compression ratio (CR) was investigated, and the relationship between the displacement and transport properties was quantified. The results show that the carbon-fiber displacement in the Z direction (through plane) under compression is more noticeable. As CR is increased to 30%, the displacement change in Z of domains A and B are -59~+5 μm and -145~+16 μm, respectively. The diffusion coefficient of the vanadium ion in XY direction is decreased by 15.4%, and in Z direction by 24.2%.The conductivity in XY direction is increased by 112.5%, and in Z direction by 113.3%. The simulation results are in good agreement with the experimental data, and the suggested domain size that can better simulate and predict the carbon felt conductivity is: X/Y=300~400 μm, and Z=200~400 μm.