An ohmic alloy system with a Cr barrier layer was optimized for GaAs ohmic contacts in this study. At 420 ℃/60 s annealing, the new alloy system, Au/Cr/AuGe/Ni, has a low specific contact resistivity of 2.63×10^-6 Ω·cm², whereas the p-type alloy system, Ti/Cr/Au, has a resistivity of 6.99×10^-7 Ω·cm² at 440 ℃/60 s annealing. Simultaneously, both structures achieved a low specific contact resistivity over a relatively wide temperature of 420-460 ℃. The XRD analysis indicates that the Cr barrier layer effectively achieves a diffusion barrier and improves the ohmic contact quality. SEM and AFM characterization results indicate that the Au/Cr/AuGe/Ni alloy system with a Cr barrier layer has a uniform and flat surface, and the Ti/Cr/Au system has good surface properties. The Au/Cr/AuGe/Ni alloy system improves significantly in ohmic contact performance compared with the conventional Au/Ni/AuGe/Ni alloy system; the Ti/Cr/Au alloy system is comparable with the Ti/Pt/Au alloy system. Thus, ohmic contact electrodes with a Cr barrier layer meet the requirements of semiconductor devices and facilitate batch use.