This study focused on the water vapor removal efficiency by the surface-modified poly(vinyl alcohol)/poly(vinylidene difluoride) (PVA/PVDF) hollow fiber composite membranes with poly(dopamine) (PDA) in the dehumidification process. Two different ways of PDA modification were experimentally investigated and examined in terms of the separation performance of water vapor. A laboratory-scale testing device was set up to measure the water vapor permeance and the water vapor/H-2 selectivity. Compared with the pristine PVA/PVDF membrane, the membrane modified using PVA/PDA mixture formed a dense and thin layer with high nitrogen solubility, which was not conducive to improve the water vapor removal efficiency. In contrast, the three-layer PDA-PVA/PVDF-modified membrane with PDA significantly enhanced the dehumidification performance. The influences of modification conditions (PDA concentration and PDA modification time) on the water vapor permeance and water vapor/H-2 selectivity of PDA-PVA/PVDF-modified membrane were further studied. The highest water vapor permeance of 2898 GPU was obtained at certain conditions (0.1 g L-1 PDA solution and modification time of 30 min). It was demonstrated that the surface modification with PDA could play an important role in enhancing the hydrophilicity and water vapor/H-2 separation performance for PVA/PVDF composite membranes.