Abstract: The potential of boron nitride nanosheets (BNNS) in thermal management materials is significantly hindered by the inherent surface chemical inertness that leads to a substantial interfacial thermal resistance. To overcome this limitation, hydroxyl-functionalized boron nitride nanosheets (BNNS-OH) were successfully synthesized through a high-temperature alkali treatment coupled with liquid-phase assisted ultrasonication. Subsequently, a vacuum filtration combined with compression drying technique was employed to fabricate BNNS-OH/CNF composites. The hydroxyl groups on the surface of BNNS enhance compatibility with CNF and improve the dispersion of BNNS, thereby reducing the interfacial thermal resistance. Furthermore, the one-dimensional structure of CNF does not fully cover the thermal fillers, and the compression drying method effectively minimizes the voids between the fillers and polymer, resulting in a dense layered structure. This facilitates better contact between fillers, forming continuous thermal conduction pathways and enhancing the thermal conductivity of the composite material. When loaded with 30wt%BNNS-OH, the thermal conductivity of the BNNS-OH/CNF composite reaches as high as 14.571 W·m⁻¹·K⁻¹, approximately 819% higher than that of pure CNF films. In practical heat dissipation applications, compared to CNF films, LED chips encapsulated with BNNS-OH/CNF composite films exhibited a temperature reduction of 29.5℃ within 150 s.