<p>The objective of this experiment was to provide a method for estimating the leakage stability of gelatin-based soft capsule shells during storage. The equilibrium moisture content of the soft capsules increases with temperature and humidity. Through FTIR spectroscopy and SEM images, it was found that the leakage phenomenon was actually due to the swelling of gelatin rather than chemical changes. Furthermore, based on the analysis of hygroscopic kinetics and macromechanics, the relationship between the rate of mass change and mechanical properties over time was investigated and the moisture absorption capacity and mechanical failure time of the soft capsules were evaluated. Importantly, the Arrhenius equation and the generalized Eyring model were established, which successfully estimated when leakage occurs under various storage conditions. The proposed models will provide valuable estimative information about the shelf life of soft capsule shells.</p>