Optical third-harmonie generation (THG) in the poly (N-vinylearbazole) (abbreviated as PVI)-fullerene combination films has been studied by using a 50 pieoseeond Nd:YAG laser as the fundamental light source at 1.06 μm. THG enhancement is observed in the PVK/C60 multilayer and mixed films compared with pure PVK and C60 films. Considering the charge-transfer (CT) process between these two materials, we attribute this third-order nonlinearity enhancement to the change of dipole moment and susceptibility caused by the carriers generated by the CT process in multilayer film. But in mixed film, the CT complex plays an important role.