We study the quantum interference in three-photon resonant nondegenerate six-wave mixing (NSWM) of a five-level system in which the middle level of six-wave mixing and other levels are coupled by a strong laser field. The coupling field-dependence of the NSWM signal intensity, and the spectrum of the NSWM with a coupling field, are discussed. We find that in the presence of a strong coupling field, the three-photon resonant NSWM spectrum exhibits Autler-Townes splitting, which reflects the levels of the dressed states. It also leads to either suppression or enhancement of the NSWM signal. Due to the enhancement of NSWM signal caused by quantum interference, the dressed state created by a coupling field can replace the atom intrinsic level and serve as the middle level of three-photon resonance. Thus the middle level of three-photon resonance can be controlled by a coupling field.