Abstarct: In this research, molecular structure, vibrational frequencies and the chemical shifts of 1HNMR of N-salicylidenaniline (NSA) were investigated by means of density functional theory (DFT) calculations and then the results were compared with the analogous parameters of 2-iminomethyl-phenol (2IMP). The effect of phenyl group on the intramulecular hydrogen bonding strength studied by the Natural Bond Orbital (NBO) analysis. IR and Raman spectra of NSA and its deuterated analogue were clearly assigned and then were compared with the calculated results. The observed OH/OD and OH/OD were appeared at about 2967/2133 and 822/583, respectively, which were consistent with the calculated geometry and proton chemical shift results. The results of NBO analysis indicated that the electron-withdrawing effect of phenyl group decreased the hydrogen bond strength, but the steric effects increased the strength of the bond, so, the hydrogen bond strength of NSA is slightly weaker than that of 2IMP.