Molecular dynamic simulations and 1 H-1 H NOESY spectroscopy have been used to study the conformations and hydrogen bond interactions of RGD tri-peptide in aqueous solution. The properties are characterized by intramolecular distances, radius of gyration, root-mean-square deviation, and solvent-accessible surface. The RGD molecule is highly flexible in aqueous solutions and the conformations can shift between extended and folded states. Most of the time, RGD exists in the extended state in aqueous solution. The results in the MD simulations and 2D-NMR experiments are in good agreement.