Abstract: Sealing failure occurred to the sensing component after the high and low temperature test of a pressure annunciator. Through failure modes analysis, simulation calculation and test, the sealing failure cause of the sensing component was explored and improvement was carried out. The results show that the attenuation of thread preload is the direct cause of the sealing failure of the sensing component. Due to the lower hardness of the shell material of the sensing component, micro-yield deformation occurred in the test, which made the thread unable to match effectively, resulting in the attenuation of the preload. Meanwhile, the difference of the relative variation of volume between the shell and the cover further boosted the attenuation of the preload of the sensing component in the test. Through improving the shell material, the attenuation of the preload of the sensing component has been effectively alleviated, and the sealing failure of this type of sensing components has been solved.