Abstract: With the rapid development of 5G/6G communication technologies, artificial intelligence (AI) chips and high-power electronic devices, high-efficiency thermal management has become the core bottleneck restricting their performance and reliability. Polymer-based thermal interface materials are widely used due to their excellent electrical insulation and processability, but their intrinsically low thermal conductivity is in urgent need of improvement. 2D materials such as graphene and h-BN possess ultra-high in-plane thermal conductivity, providing an effective route for the fabrication of high-performance thermally conductive composites. However, the ITR between 2D materials and the polymer matrix severely hinders the full realization of their thermal conductivity potential. Most existing relevant reviews mainly focus on the overall research of thermally conductive polymer composites and the application expansion of 2D fillers, while there is still a lack of systematic and thematic reviews targeting the regulation of thermal transport mechanism of interfacial modification layers in 2D material-polymer thermally conductive composites. This review systematically focuses on the interfacial modification layer strategies and their regulation of thermal transport mechanisms in 2D material/polymer thermally conductive composites. Based on phonon transport theory, it elaborates the formation mechanism and quantitative models of ITR, summarizes the latest advances in covalent, non-covalent and hybrid modification, and elucidates the underlying mechanism of various modification layers in reducing ITR. Meanwhile, it discusses the applications of in-situ characterization techniques, multi-scale simulation and machine learning-assisted prediction methods. Combined with practical industrial requirements, this review summarizes the key challenges in the field and prospects the future development directions, so as to provide support for the design of next-generation composite materials with ultra-low ITR and customizable thermal conductivity.