To meet the higher requirements posed by high-power chips on packaging materials, designing and fabricating a multi-functional integrated composite is an effective solution. In this work, the diamond/Ag hybrid filler was prepared (in-suit growth) using the “Ball milling-Heating” approach in the absence of any solvent or external force. Furthermore, the nano-micro hybrid filler was combined with the inherently high thermal conductivity liquid crystal epoxy resin to create composites through a hot-press curing. In this process, there is a synergistic interaction between fillers and matrix and Ag nanoparticles serve as bridging elements in nano-scale. Ultimately, the hybrid filler with a nano-microstructure effectively constructs “phonon-electronic-phonon” pathways in the liquid crystal epoxy matrix. When the hybrid filler content reached 80 wt%, the composites demonstrated a range of integrated advantages including high thermal conductivity (4.65 W/m·K), low coefficient of thermal expansion (CTE), high volume resistivity, and excellent thermal stability. The era of high-power devices is approaching, and this study offers a novel perspective on the application of epoxy-based composite materials in the realm of advanced packaging.