The lattice kinetic Monte Carlo simulation (kMCS) was applied to study the boron diffusion in Si-SiGe beyond nanotechnology. Both the interstitialcy and kick-out mechanisms of boron diffusion were considered, including the effects of annealing temperatures, boron dopant concentrations, Ge compositions, and concentrations of Si self-interstitial defects (SiI). The effects on boron diffusion caused by single and double layer(s) of SiGe phase with different Ge contents and varying boron concentrations in double layers of SiGe phase were also simulated. The results show that boron diffusion in Si and between SiGe-Si both largely increase as the temperature or concentration of SiI increases, but the boron diffusion between SiGe-Si is much less than in Si. Increasing the Ge contents in SiGe alloy could retard boron diffusion heavily, while increasing the boron concentration on SiGe phase would enhance boron diffusion.