The lithium absorption energies and electronic structures of the boron-doped single-walled carbon nanotubes (SWCNT) were investigated using the first-principles calculations. The lithium absorption energies in the B-doped SWCNTs are large negative values, compared with those in the pure SWCNT, whether Li is absorbed at inner sites or at outer sites of the tube walls. The B doping forms an electron-deficient structure in SWCNT, which can effectively accept the electrons from the absorbed Li and stabilize the Li absorption on the tube wall. The calculation results suggest that enhanced Li absorption capability in the B-doped SWCNT should be expected.