The solvation structure of 1,3-butanediol (1,3-BD) in aquedus binary Solvents of acetonitrile (AN), 1,4dioxane (DIO), and dimethyl sulfoxide (DMSO) at various mole fractions of organic solvent x(os) has been clarified by means of infrared (IR) and H-1 arid C-13 NMR. The change in the wavenumber of O-H stretching vibration of 1,3-BD in the three systems suggested that water molecules which are initially hydrogen-bonded with the 1,3-BD hydroxyl groups in the water solvent (x(os) = 0) are more significantly replaced by organic solvent molecules in the order of DMSO >> DIO > AN. This agrees with the order of the electron donicities of the organic solvents. The H-1 and C-13 chemical shifts of 1,3-BD also revealed the most remarkable replacement of water molecules on the hydroxyl groups by DMSO. In contrast to the DMSO system, the O-H vibration band of 1,3-BD in the AN and DIO systems suggested the formation of the intramolecular hydrogen bond between the two hydroxyl groups of 1,3-BD above x(os) = similar to 0.9. To further evaluate the intramolecular hydrogen bonding of 1,3-BD in AN water binary solVents, molecular dynamics (MD) simulations and NMR experiments for spin lattice relaxation times T-1 and H-1-H-1 nuclear Overhauser effect (NOE) were conducted on 1,3=-BD in the AN system. These results showed the intramolecular hydrogen bond within 1,3-BD in the AN water binary solvents in the high AN mole fraction range of x(AN) > 0.9. Especially, the pair correlation functions g(r) of the OH-O interactions of 1,3-BD obtained from the MD simulations indicated that the iritramolecular hydrogen bond remarkably increases in the AN solvent as the x(AN) rises to the unity.