The aim of this work was to study the material selection and packaging thickness design of the knock-out drum in gas support equipment for air to air missile, to verify the reliability and use it as an evaluation index for the equipment. At first, the possible press on the knock-out drum was theoretically calculated and then Solidworks was used to build a model and definite the material type. Because this equipment is operated in extremely cold or high-temperature environment, the effect of temperature on the packaging material was analyzed by Ansys material thermal analysis. At last, 1/4 surface of the packaging drum was selected for finite element analysis of stress and displacement, and its displacement variation diagram was obtained. The numerical result was contrasted with the overall thickness of the knock-out drum to analyze its reliability. The steel material selected had good thermal conductivity and did not lead to thermal difference. The displacement resulted from the maximum stress load on the packaging surface was 2.1% of the thickness. The reliability was good. In conclusion, the knock-out drum surface packaged by Q235-B had good reliability, and can be manufactured. This analysis process could provide reference for the reliability analysis for other units of the equipment.