Abstract: To make the electrode reactants and products in the proton exchange membrane fuel electricity (PEMFC) more stable and evenly distributed, in this study, based on the traditional cathode serpentine flow channel of fuel cells, the inlet and outlet of the U-turn are gradually tapered and expanded, and the side wall of which was made to form a certain slope angle. A three-dimensional numerical model of a single cell with a tapered and expanded slope flow channel was established. The effects of different geometrical parameters on the kinetic behavior of liquid water in the flow channel, drainage efficiency, reaction gas mass fraction, and maximum power density of the cell were studied comparatively. The results showed that the slope structure guided the flow path of droplets, and the airflow perturbation near the bottom surface Gas Diffusion Layer (GDL) of the flow channel was enhanced. The oxygen mass fraction and current density were shown to be more uniformly distributed, and the maximum power density and the overall mass transfer capacity inside the PEMFC were improved.