Sourdough is a mixture of flour and water， including microorganisms such as yeast， lactic acid bacteria （LAB） and mold. The pasta products fermented by sourdough have been deeply loved by people in recent years. In order to understand the basic characteristics of LAB isolated from traditional sourdough， a series of test methods were used in this paper， such as DNA extraction and construction of phylogenetic tree， microscope observation， infrared spectroscopic analysis， growth and growth curve determination， pH value and acid production curve determination， biochemical properties identifcation， antibacterial and drug susceptibility test. The identification results indicated that the LAB was Lactobacillus sanfranciscensis， a gram-positive bacteria， catalase was negative， and the bacteria was rod-shaped. Fourier transform infrared spectroscopy was used to analyze the cell components of bacteria including fatty acids， proteins， polysaccharides and other substances. The biomass of L. sanfranciscensis was （24 ± 1） g/L， the reproductive algebra was 0.36， the growth rate constant was 0.045， the generation time was 22.42 min， the lowest pH was 4.09 ± 0.01， and the total acidity was （0.70 ± 0.01） g/L. It can utilize maltose， and the degree of sucrose utilization has differences in bacterial species. It has inhibitory effects on Staphylococcus aureus， Escherichia coli and Candida albicans. And the 30 antibiotics tested have different effects on L. sanfranciscensis. A strain of high-yield exopolysaccharide LAB SXU-1001 was L. sanfranciscensis， which was the dominant LAB in traditional sourdough， and provided a reference for the development of LAB resources in sourdough.