Mannans were extracted from S. cerevisiae, the rheological properties of mannan solutions were important in many industrial applications. In this paper, effects of mannans concentration, solution temperature, pH, type of salts and their concentrations on apparent viscosity were investigated. The conformational parameters of yeast mannas were determined by SEC-MALS-RI-DP. The Higiro's 1 and Higiro's 2 plots obtained by capillary viscometry gave an intrinsic viscosity of 0.166 and 0.131dl/g. The yeast mannan solution showed Newtonian flow behavior at all the tested concentrations. The apparent viscosity of yeast mannans solution decreased continuously with increase in temperature (25°C-85°C) at a given shear rate. The viscosity did not change within the pH values of 4.0 to 10.0, however, it increased when the pH decreased from 4.0 to 2.0. The viscosity decreased with addition of CaCl2 up to 10mM and remained constant above this concentration. The conformational parameters (derived from [η] vs Mw and Rg vs Mw) showed yeast mannans existed as a sphere-like shape with many shorter branches. The special flow behavior and conformation of yeast mannans may make it preferable polysaccharide in food industry.