Microbial exopolysaccharides secreted by microorganisms during metabolic processes have been widely used in biotechnology because of their environmentally friendly and renewable nature. This study evaluates the potential of a novel microbial exopolysaccharide, diutan gum, which is produced by Sphingomonas species, for enhanced heavy oil recovery at high temperature and high salinity. In addition, two conventional polymers [xanthan gum and partially hydrolyzed polyacrylamide (HPAM)] used in oil exploitation are compared under the same conditions. It is found that the steady apparent viscosity and dynamic modulus of aqueous diutan gum solutions are not sensitive to the temperature and virtually independent of the salinity, while those of xanthan gum and HPAM significantly decrease at high temperature and high salinity. The retention values of the apparent viscosity and the dynamic modulus of diutan gum at 90 degrees C and 244 121 mg.L-1 salinity are greater than 90%. The gel like structure of diutan gum is dependent on the shear rate rather than the shear time and the aging time. The thermal stability and salt tolerance of diutan gum are mainly attributed to the stability of the gel-like molecular structure, which is greatly related to the double helix. Flow tests in sandpacks demonstrate the excellent mobility control capacity of diutan gum in porous media, and the permeability reduction of porous media is attributed to the adsorption and interception of diutan gum at high temperature and high salinity. Sandpack flooding experiments confirm that the heavy oil recovery efficiency of diutan gum is raised by 20.9% OOIP and is higher than that of either xanthan gum (9.3%) or HPAM (5.4%) at 90 degrees C and 244 121 mg.L-1 salinity. It is believed that diutan gum will be a promising oil recovery agent for enhanced oil recovery in high-temperature and high-salinity reservoirs.