Single-electron lithium bond complexes CH3…Li—CH3(I), H3CH2C…Li—CH3(II), (H3C)2HC…Li—CH3 (III), and (H3C)3C…Li—CH3(IV) were investigated at the B3LYP/6-311++G(d,p) and MP2/6-311++G(d,p) levels of density functional theory. Results showed that the single-electron lithium bond strength of the complexes H3CH2C…Li—CH3(II), (H3C)2HC…Li—CH3(III), and (H3C)3C…Li—CH3(IV) increased in the following order: II (-26.7 kJ·mol-1)<III(-30.2 kJ·mol-1)<IV(-32.8 kJ·mol-1). By comparison to the monomer Li—CH3, the vibrational frequencies of Li—CH3 in complexes II, III, and IV were abnormally blue-shifted by 15.1, 18.9, and 20.5 cm-1, respectively. The Li—CH3 bond was also elongated. The number of CH3 in electron donors was more, the single-electron interactions were stronger. As the H atom in the electron acceptor LiH was replaced with CH3, the interaction strength weakened. Additionally, we studied the characteristics of these complexes by nature bond orbital (NBO) and atom in molecules (AIM) methods.