The inclusion complex of β-cyclodextrin(β-CD) and sulfurized isobutylene(T321) was prepared with a co-precipitation method. The tribological properties of the complex with different concentrations were investigated by a four-ball tester in the solution of polyethylene glycol-600(PEG-600). The experimental results suggest that the complex exhibits better anti-friction and anti-wear properties than β-CD under different load conditions. The tribo-system shows the least friction coefficient when the concentration of the complex is 0.8%. During the friction process, the complex was decomposed into various molecular fragments and the T321 molecules were released onto the friction interface to provide effective lubrication. The XPS analytical results on the worn surfaces reveal that sulfide film formed by the released T321 plays a major role, and the iron alkoxide and carbon deposition films formed by the β-CD fragments have better anti-friction effect on the sulfide film surface. The interactions of different films result in the formation of a mixed boundary lubrication film. The inclusion complex of β-cyclodextrin (β-CD) and sulfurized isobutylene (T321) was prepared with a co-precipitation method. The tribological properties of the complex with different concentrations were investigated by a four-ball tester in the solution of polyethylene glycol -600 (PEG-600). The experimental results suggest that the complex exhibits better anti-friction and anti-wear properties than β-CD under different load conditions. The tribo-system shows the least friction coefficient when the concentration of the complex is 0.8%. During the friction process, the complex was decomposed into various molecular fragments and the T321 molecules were released onto the friction interface to provide effective lubrication. The XPS analytical results on the worn surfaces reveal that the sulfide film formed by the released T321 plays a major role, and the iron alkoxide and carbon deposition films formed by the β-CD fragments have better anti-friction effect on the sulfide film surface. The int eractions of different films result in the formation of a mixed boundary lubrication film.