In recent years, thermally conductive polymer-based composites have garnered significant attention due to their light weight and easy formation process. In this work, the thermal conductivity of ultra high molecular weight polyethylene (UPE) composites was improved through construction of a hybrid filler network of boron nitride sheets (BNs) and carbon nanotubes (CNTs) in the matrix via hot compression. The morphology, UPE aggregate structure, thermal conductivity, heat dissipation capacity and thermal stability of the UPE composites were investigated. The thermal conduction mechanism of the UPE composites was explored through simulations with Agari's semi-empirical formula. The results showed that the thermal conductivity of the UPE composite with 40 wt% BNs and 7 wt% CNTs was 2.38 W m⁻¹ K⁻¹, which was 495% higher than that of pure UPE, showing a synergistic effect between BNs and CNTs. The simulations with Agari's semi-empirical simulation suggested that increasing the CNT content contributed to synergistically assist BNs to form a better continuous and effective hybrid filler thermal network, thereby reducing phonon scattering and thermal resistance between BNs. In addition, UPE composites doped with BNs and CNTs presented better heat dissipation capacity and higher thermal stability as compared to that of pure UPE.