This paper concerned with design of constant stress accelerated lift test(ALT1. Becase a major factor to affect a life of automotive V-ribbed belts is a temperature, we selected a temperature as a accelerated factor to perform a test. Accelelerated life test plans were developed with the assumption of weibull lifetime distribution. The genreal value of beta parameter was accepted in this life test (β=1.1). The sample number was calculated by alpha parameter which was induced by beta.