Abstract: The bonding wire failure is one of the typical failure modes of the device. The temperature distribution on the surface of the chip has a temperature gradient, so the thermal stress experienced by each key foot is also different. Deciding whether the life of the chip depends on the key foot that bears the highest stress has always been difficult. This paper will break away from the finite element simulation analysis method of the stress-lifetime relationship, and focus on the influence of the temperature gradient on the chip surface of the lifetime of the chip. By extracting the characteristics of the temperature gradient, an equivalent experiment is designed to deeply study the influence of different temperature gradients on the lifetime of the chip under different failure modes. Taking the full-bridge device for electric vehicles as the research object, the failure mode of the device is explored through the power cycling test, and the temperature gradient characteristics of the chip surface are extracted by finite element analysis. Furthermore, by studying the temperature distribution characteristics of discrete device bond feet, the lifetime differences of different failure modes and different temperature gradients are verified. Finally, it is found that the temperature gradient will reduce the lifetime of the device only when the solder layer degradation of the device occurs, and the lifetime is shorter as the temperature gradient increases.