SF6 gas density meter, as an important monitoring equipment of primary equipment in power grid system, its reliability is related to the safe operation of substation equipment. In order to ensure the reliable operation of SF6 gas density meter, it is necessary to evaluate its reliability and life, and the constant stress accelerated life test method is one of the effective methods to evaluate the reliability of structurally complex mechanical products. This paper analyzes the accelerated stress and normal stress level of SF6 gas density meter, determines the multi-stress accelerated life test program, and uses the Weibull life-stress model to comprehensively estimate the median life, characteristic life, reliable life, average life, and the corresponding failure rate of the SF6 gas density meter, and obtains the reliability curve of the SF6 gas density meter under the normal stress, which provides a theoretical basis and data reference for the manufacture and use of SF6 gas density meter.