Abstract: Production improvement and function exploration of microbial extracellular polysaccharides are very important for the current study on natural polysaccharides. In this paper, based on a novel bacterial species type strain Rufibacter sediminis H-1 isolated and identified in our laboratory, the yield of exopolysaccharide was determined by sulfuric acid and phenol method. The fermentation conditions were optimized by single factor and response surface methodology experiments, and its emulsification and moisturizing properties were studied. According to the results of the single factor test, the factors that had a significant effect on the production of extracellular polysaccharide by strain H-1 were screened out as independent variables, and the response surface test was carried out through the Box-Behnken central combination design. Exopolysaccharide was dissolved in glycerol, hyaluronic acid, and distilled water to the concentration of 5 g/L solution, Tween 80 was used as a positive control, and an equal amount of hydrophobic substrate (olive oil, gasoline, soybean oil, rapeseed oil or xylene) was mixed with exopolysaccharides at 3∶ 2 (V/V) with a high-speed homogenizer. Then, the mixture was left standing at room temperature for 12, 24, 36 and 48 h, and the emulsification rate was the ratio of the volume of the emulsified layer to the total volume. The results indicated that the best sugar production conditions of strain R. sediminis H-1 were temperature 27.5 ℃, inoculation amount 8.5%, trehalose 2.6 g/L, yeast extract powder 1.50 g/L, pH value 7.0, its yield of exopolysaccharide was 140.49 mg/L. The moisturizing rate of the polysaccharide was still 82% at 48 h, which was close to those of glycerol and hyaluronic acid; the emulsification rates of the polysaccharides for olive oil, gasoline, soybean oil, xylene and rapeseed oil were 92.85%, 97.43%, 98.57%, 50.28%, and 34.28%, respectively. The yield of polysaccharides from R. sediminis H-1 was obviously increased after the optimization of fermentation condition. The polysaccharide product showed a good moisturizing and emulsification effect and emulsion stability for some oils and hydrocarbons.