We have designed and synthesized a Schiff base ligand. N,N'-bis(o-hydroxybenzylidene)diethylenetriamine, as a host that exhibits the strong binding ability to salicylaldehyde as a guest. The binding characteristics of the interaction between the Schiff base and salicylaldehyde have been obtained by NMR spectroscopy study. The reversible binding mechanism depending upon the solution pH has been monitored by NMR spectroscopy during the acid titration reaction. The interaction between the schiff base and salicylaldehyde was also confirmed by COSY and NOE experiments.