The lithium absorption energies and electronic structures of boron- or silicon-doped single-walled carbon nanotubes (SWCNT) were investigated using ﬁrst-principles calculations based on the density-functional theory. As B and Si doping carbon nanotubes, the lithium atom adsorption energies decrease. The effects of B and Si doping are different on the lithium atomic adsorption. B-doping forms an electron-deﬁcient structure in SWCNT. While the Si-doping forms a highly reactive center. The calculations suggest that boron- and silicon-doping in SWCNT will improve Li absorption performance.