<p>The sensitivity of nitrocellulose (NC) has a significant influence on the vulnerability of NC-based gun propellants. Thus, reducing the sensitivity of NC is important, and the study of the underlying mechanisms and factors influencing their sensitivity is foundational for the preparation of insensitive NC. In this work, the mechanical mechanisms and factors influencing NC sensitivity were studied by the density functional theory, SEM, TEM, XRD, TGA, DSC and drop hammer experiments. The results showed that the sensitivity of NC is related to the dissociation energy of the O–NO₂ bonds. Moreover, the crystal structure, morphology, and size contribute to the impact sensitivity of NC. The effects of morphology and size on impact sensitivity are more significant than those of crystal structure, but they only hardly affect friction sensitivity. The friction sensitivity of NC is affected by the internal friction among NC chains. This research reveals the underlying mechanism of the mechanical sensitivity of NC, providing a theoretical basis for the desensitization of this material.</p>