In this study, we investigate the coupling of an internal field (defect field-sp³ bonds and nanopores) and an external field (strain and temperature). Simultaneously, we provide a design idea of hybrid materials. The mechanical properties of hybrid materials under the condition of internal and external field coupling were studied. When nanopores and sp³ bonds are considered simultaneously, we found that internal (sp³ bonds and defects) and external field (temperature and strain fields) have a negative chain reaction on the mechanical properties of BN–graphene–BN/BN vertically-stacked nanostructures, and the negative chain reaction will gradually increase with the change in parameters (such as the increase in temperature). The sp³ bonds can be regarded as a special defect, which will increase the initial strain of the system. In addition, the mechanical properties of the nanostructure, containing square nanopores in the boron nitride region are most sensitive to temperature change, relative to the nanopore in the other two regions. Atoms (around square nanopores) are more likely to overcome the binding energy and lose stability from the inherent equilibrium position, relative to that of circular nanopores.