▎ 摘　　要

The design of graphene-based composite with high thermal conductivity requires a comprehensive understanding of phonon coupling in nanosized graphene. We extended the two-temperature mod-el to coupled groups of phonons. The study give new physical quantities, the phonon phonon coupling factor and length, to characterize the couplings quantitatively. Besides, our proposed coupling length has an obvious dependence on system size. Our studies can not only observe the nonequilibrium between different groups of phonons but explain theoretically the thermal resistance inside nanosized graphene.