Abstract: A novel multi-layered metalliation structure (Au/pt/TiN/Ti/PtSi, TiN as barrier)was applied to the high power microwave transistor, which was compared with the application of old structure (Mo and W as Barrier). The experiments indicate that the Mean Time to Failure (MTF) of sample with TiN barrier is twice as much as that of sample with W barrier under high temperature and high current density conditions.The heat endurance tests show that samples with TiN and W barrier can endure higher temperature than samples with Mo barrier.