The contact angle hysteresis is an important parameter influencing the micro-size droplet wetting on the solid surface. In this study, a theoretical method for calculating the contact angle hysteresis of a moving water droplet on the gas diffusion layer (GDL) surface in a proton exchange membrane (PEM) fuel cell flow channel is developed through the force analysis. Correlations for the contact angle hysteresis are investigated. It is found that the contact angle hysteresis increases with the sliding angle, the static contact angle and the water droplet size. The contact angle hysteresis is also influenced by the water spreading shape and the distribution of the dynamic contact angle.