The resonance enhanced multiphoton ionization method has been applied to the study of NO-Ar van der Waals complex in the nsσ (n = 3,4) Rydberg states. We have assigned the intermolecular vibrations appearing in the ×X˜ excitation spectrum of the complex. The bending structure appeared only with the excitation of the stretching mode in the à state, which was interpreted by intermolecular forces. The E˜-à excitation spectra were independent of the initial intermolecular level in the à state and the dissociation threshold to NO(E2+ ) + Ar was determined to be 60950 cm-1. The s–d mixing in the 4sσ orbital would make the intermolecular vibrational structure in the E˜—Ãspectra complex.