This study uses fuel cell gas diffusion layers (GDLs) fabricated in the laboratory from carbon fiber cloth with different concentrations of hydrophobic agents in proton exchange membrane fuel cells (PEMFCs), and investigates the relationship between the hydrophobic agent content of the carbon fiber cloth and fuel cell performance. The paper examines the effect of hydrophobic agent content on GDL thickness, contact angle, air permeability, and surface and through-plane resistivity. Carbon fiber cloth is impregnated with hydrophobic agent concentrations of 0, 3, 5, 10, 30, and 50wt%, and the resulting GDLs are subjected to performance tests. When the test piece area is 25cm2, the test temperature 80°C, the gasket thickness 0.36mm, and the hydrophobic agent content 5wt%, a fuel cell using the GDL has a current density of 1430mAcm−2 at 0.3V.