A process for preparing the gallium nitride-based semiconductor device of the compound in III-V famility includes such steps as generating the stacked semiconductor structure on substrate. The substrate is composed of n-type semiconductor layer, active layer and p-type semiconductor layer, etching to expose part of n-type semiconductor layer, generating the first electrode consisting of ohm contact layer and barrier layer as well as weld pad layer, anneling, activating p-type semiconductor layer and generating the second electrode.