The thermal conductivity (TC) of non-periodic Si/Ge superlattice nanowire (SLNW) is investigated by non-equilibrium molecular dynamics simulation (NEMD). It is found that the TC of non-periodic Si/Ge SLNW can be significantly reduced at room temperature. Compared to the minimum TC of periodic Si/Ge SLNWand pure Si nanowire, the TC of non-periodic Si/Ge SLNW is further decreased to be around 47.4%, 4.4% of that of periodic Si/Ge SLNW and pure Si nanowire respectively. By introducing 20% Ge atom doping, the TC of non-periodic Si/Ge SLNW with 10-unit cell (UC) thickness is reduced by 38%. The reduction of TC of non-period Si/Ge SLNW is first due to the destruction of phonon coherent transport. Additionally, the change of periodic length can cause shift of density of state (DOS), which makes the interface of Si/Ge with different lengths play roles to scatter the phonon with different wavelengths. Therefore, the distribution of thickness from atomic to nano scale can decrease the TC by scattering phonon with more wavelengths. The results provide an efficient way for future thermoelectric applications. (C) 2018 Published by Elsevier Ltd.