The microporous layer (MPL) of proton exchange membrane fuel cells (PEMFCs) plays an important role in the transport of water, gas, heat and charge. Mechanical deformation and microstructural damage can significantly impair these transport processes. In this study, the stress-strain relationship of the MPL was experimentally determined after material fabrication and microstructural characterization. A numerical reconstruction of the MPL was then developed based on the extracted microstructural parameters, and finite element simulations were conducted to evaluate the displacement-stress distributions of carbon particles and polytetrafluoroethylene (PTFE) under different mechanical strains. Results show that mechanical loading induces substantial strain within the MPL, with the highest stress occurring at the surface, where stress concentration is most likely to form. Stress was found to increase exponentially with applied strain. At 10% strain, the maximum stress on carbon particles and PTFE was about 31.385 MPa and 14.873 MPa, respectively; when strain increased to 40%, the corresponding stresses rose to 160.03 MPa and 96.165 MPa, accompanied by a pronounced intensification of stress concentration regions.