Thermal management issue has been a bottleneck with the development of modern electronics towards higher speed, miniaturization and functionalization. To address this problem, novel polymer composites with improved thermal conductivity is strongly demanded. However, traditional polymer composites with roughly designed structure and high filler content usually cannot meet the increasing requirements. In this work, hierarchical epoxy/oriented BN-SCMC (Sodium Carboxymethylcellulose) polymer composites with well-interconnected structure were successfully exploited by freeze casting and infiltrating methods. The pre-formed three-dimensional (3D) BN scaffold endows the prepared composites an enhanced in-plane thermal conductivity (4.24 W m −1 K −1 ) at 34.2 vol% BN loading. In addition, the influence of SCMC content on the morphology and thermal conductivity of composites was further investigated.