Three kinds of yeast mannan with different molecular weights, namely YM-30, YM-50 and YM-90, were prepared by extracting with water in high temperature and ethanol precipitation fractionation. The weight average molecular weights, solubility, pH and viscosity of three kinds of yeast mannan were determined, and their hygroscopicity and moisture retention were investigated. The results show that the weight average molecular weights of YM-30, YM-50 and YM-90 were 12.40×104 Da, 4.47×104 Da and 2.16×104 Da respectively. YM-30 with large molecular weight was not soluble or slight soluble in water, but YM-50 with medium molecular weight and YM-90 with small molecular weight were soluble in water. YM-30 solution was weakly-alkaline and YM-50 solution was neutral, but YM-90 solution was weakly-acidic. The solutions of YM-50 and YM-90 had very low viscosity which was almost the same that of water. Furthermore, their viscosities were not influenced by mannan concentration and temperature. The infrared spectroscopy spectra showed that the polysaccharide chains of three yeast mannan were β-D-pyran type structure. Under the condition of low moisture (RH 43%), YM-90 had the strongest moisture absorbability. However, under condition of high moisture (RH 81%), the moisture absorbability of YM-30 was the best. Under the environment of RH 43%, moisture retention of YM-30 was the best, and its moisture retention ratio was 98.4%, which was slightly higher than that of hyaluronic acid. Yeast mannan from Saccharomyces cerevisiae had perfect moisturizing performance.