The fractal tree-shaped network is introduced to reconstruct the Si/Ge nanocomposites in this paper with a focus on reducing the thermal conductivity of thermo-electrical materials by enhancement of phonon scattering at the interfaces of nanostructures. The molecular dynamics simulation with the use of the empirical Tersoff potential is applied to study the thermal conductivity of Si/Ge nanocomposites with fractal tree-shaped networks. The effects of fractal dimensions and branch level on the thermal conductivity of nanocomposites are evaluated and analyzed. The results indicate that, compared with conventional rectangular core, the fractal tree-shaped network is more superior in the reduction of thermal conductivity of nanocomposites owing to stronger phonon interface scattering for larger interface density. In particular, the larger length and width fractal dimensions as well as more branch levels are preferred for the Si/Ge nanocomposites with fractal tree-shaped networks. (C) 2015 Elsevier Ltd. All rights reserved.