In this paper,the basic structure and properties of Sanxan gum are investigated. The results of infrared spectroscopy and rheological property analysis show that the molecular structure of Sanxan gum contains a large amount of conjugated hydroxyl groups and has a structure with a pyranose ring as the skeleton connected by glycosidic bonds in both α-and β-configurations,which is in line with the structural characteristics of polysaccharides. It shows a weak gel structure when the concentration of Sanxan gum is higher than 0.3%. The rheological properties,texture properties,particle size distribution,sensory evaluation and microstructure of low-fat salad dressing with different concentrations of Sanxan gum are studied.The results show that Sanxan gum could maintain the stability of low-fat salad dressing emulsion due to its thickening,emulsification and certain weak gel properties,as well as maintain the taste similar to the high-fat product,making it a good fat substitute.