This study presented the effect of membrane thickness on hydrogen permeability. Microvoids on the surface of the membrane should not exist for the exact values of hydrogen permeability. Pd-Cu-Ni hydrogen alloy membranes were fabricated by Ni powder sintering, substrate plasma pretreatment, sputtering and Cu reflow process. And this leaded to void-free surface and dense film of Pd-Cu-Ni hydrogen alloy membrane. Hydrogen permeation test showed that hydrogen permeability increased from 2.7 to $15.2ml/cm^2{cdot}min{cdot}atm^{0.5}$ as membrane thickness decreased from 12 to $4{mu}m$. This represented the similar trend as a hydrogen permeability of pure palladium membrane based on solution-diffusion mechanism.