Abstract： The neck gasket is the core component of the container and closure system for metered dose inhaler(MDI).When the neck gasket has been exposed to the liquid organic excipients for a long time,gasket swelling will directly affect the rate of environmental moisture ingress into the sealing system and indirectly affect the impurity level of the drug.In this study,industrial computerized tomography(CT)technology was used to detect gasket swelling behavior of the marketed beclometasone dipropionate inhalation aerosol samples in the upright and inverted orientations in the long-term stability test,and critical quality attributes such as delivered dose per actuation,fine particles dose(FPD),and related substances were also evaluated.The results showed that the hydrolysis impurity H levels in the inverted stability samples were significantly lower than those of the upright samples in the long-term stability test,and the interaction between neck gaskets and formulations had no obvious effect on other critical quality attributes such as leak rate,delivered dose per actuation,FPD,and medication actuations per container,which were consistent with the standard of the 2020 edition of Chinese pharmacopoeia.