A rapid evaluation method. temperature ramp method, for GaAs MESFETs ohmic contacts is proposed, and an automatic evaluation system has been developed. By use of this method and system, activation energy for ohmic contacts degradation can be obtained using less time and a small number of samples than traditional method, and the results are in agreement with those obtained by traditional methods. In accordance with some drawbacks of traditional AuGeNi/Au ohmic contacts, a new ohmic contacts system with TiN diffusion barrier layer is proposed. Experiment results show that the reliability of ohmic contacts with TiN is greatly superior to that of traditional AuGeNi/Au ohmic contacts.