Although the hygroscopicity of a NaNO3/water microdroplet and a polyalcohol/water microdroplet, two of the most important aerosols in atmosphere, has been widely studied, little is known about the relationship between the hygroscopic behavior of mixed NaNO3/polyalcohol/water droplets and their structures on the molecular level. In this study, the hygroscopicity of mixed glycerol/NaNO3/water droplets deposited on a hydrophobic substrate was studied by micro-Raman spectroscopy with organic-to-inorganic molar ratios (OIRs) of 0.5, 1, and 2. In the mixed glycerol/NaNO3/water droplets, glycerol molecules tended to combine with Na+ and NO3- ions by electrostatic interaction and hydrogen bonding, respectively. On the basis of the analyses of the changes of symmetric stretching (v(s)-CH2), asymmetric stretching (v(a)-CH2), their area ratio (Av(a)-CH2/Av(s)-CH2) of glycerol, and symmetric stretching band of NO3- (v(1)-NO3-) with relative humidity (RH), it was found that the conformation of glycerol was transformed from alpha alpha mainly to gamma gamma and partly to alpha gamma with a decreasing RH in the mixed droplets, contrary to the case in the glycerol/water droplet. In addition, the glycerol with gamma gamma and alpha gamma conformation had strong interaction with Na+ and NO3- respectively, which suppressed the formation of contact of ions and delayed the efflorescence relative humidity (ERR) for the mixed droplets compared to the NaNO3/water droplet.