Au heater is one of the core components of thermo optic effect devices. The reliability of Au heaters affects the lifetime of whole devices directly. In order to explore the influence of shape parameters on lifetime of Au heater, the accelerate life test (ALT) was designed and conducted. Samples with different shape parameters were prepared for the ALT in which the applied current was 500mA and the test temperature was 150°C. The results showed that failure mode of all the different samples was open circuit. The electromigration was found the reason for this kind of failure in test conditions. According to the experimental and finite element simulating results, the fusing break appeared in the transition arc area where temperature gradient was the maximum. It is also can be found that the larger the radius, the later the failure. In other words, lifetime of the thin-film heater with larger transition radius was longer.