Staphylococcus aureus infection is a global public health problem, searching and developing green alternatives for antibiotics are urgently required. In this study, the exopolysaccharides (EPS) produced by Lactobacillus helveticus WXD191 were extracted and purified. Structure analysis suggested that the EPS contained Ara, Man, Gal, GalN, Glc, GlcN, and GlcA, with a molecular of 84.2 kDa. Methylation combined with nuclear magnetic resonance (NMR) spectroscopy analysis revealed that the backbone of EPS was →3)- β-D-Galp-(1→3)-β-D-GlcpNAc-(1→4)-β-D-GlcpA-(1→3-Man-1→2-Man-1→2,6-Man-1→2,6-Man-1→. Congo red analysis and circular dichroism (CD) spectrum indicated the existence of α-helices. Crystalline characteristics, scanning electron microscopy, and thermogravimetric analysis revealed that EPS formed thermally stable amorphous with a small amount of microcrystalline structure and a rough and porous surface. Meanwhile, the S. aureus bloodstream infection model was used to evaluate the protection efficiency for systemic infection induced by S. aureus and found that the EPS could enhance survival as well as reduce bacterial burden and proinflammatory chemokines. Collectively, these results suggested that EPS isolated from L. helveticus was a competitive candidate for defense against S. aureus infection.