Droplet purging in the gas diffusion layer (GDL) is the key to improving the performance of proton exchange membrane fuel cells (PEMFCs). Lattice Boltzmann method (LBM) is used to study the dynamic behavior of multiple droplets randomly distributed in the GDL under air purging. The GDL is randomly reconstructed. The effects of rib width, initial water content, contact angle and air velocity are studied. By analyzing the dynamic distribution of droplets in the GDL and the change of the remaining water content with time, it is found that the droplets are only a small amount under the rib and accumulated mostly on both sides of the GDL at stabilization, which is caused by the large velocity under the rib. The residual water content in the GDL increases with the increase of the initial water content, and decreases with the increase of the rib width, contact angle and air velocity. However, when the rib to channel width ratio exceeds 1, the improvement of purging effect is not obvious, the purging time increases significantly, and the increase of air velocity does not help much to remove the droplets accumulated on both sides of the GDL.