Objective For exploring new environmentally friendly metal surface protection measures, corrosion inhibition of extracellular polymeric substances (EPS) of lactobacillus reuteri on carbon steel was researched. Method By corrosion weight loss method, X-ray diffraction (XRD) and scanning electron microscope (SEM), corrosion rates, corrosion products and interface morphology structure of carbon steel coupons with or without dip-coated EPS of lactobacillus reuteri were analysized. Results EPS of lactobacillus reuteri reduced the average corrosion rate of carbon steel by 25.60%. Whether with EPS or without EPS, both coupons had the same types of corrosion products. However, the proportion of magnetite, maghemite and lepidocrocite was significantly different. On the first nine days, the magnetite/ maghemite/ lepidocrocite ratio on the coupons with EPS remained in 1.0:1.0:1.1. In addition, compared with coupons without EPS, corrosion products combined with the carbon steel surface more firmly, and less rarely fell off. Conclusion EPS of lactobacillus reuteri onto carbon steel can effectively inhibit corrosion; the impacts of EPS of lactobacillus reuteri on the crystal transformation and the stability of the corrosion products of carbon steel are the main reasons for inhibition of carbon steel corrosion.