The aim of this study was to evaluate the biological characteristics and in vitro probiotic function of Lactobacillus reuteri P2M1 from swine, to determine the probiotic potential of the strain, and explore the possibility of its application in livestock production. In this study, a strain of lactic acid bacteria (P2M1) isolated from healthy pig feces was biochemically identified, and molecular biological identification was performed using bacterial 16S rDNA sequence PCR amplification and sequencing techniques. The growth curve and acid production curve of the strain were drawn to evaluate the tolerance of the strain to acid and bile salts, and the sensitivity of the strain to antibiotics was detected. The free radical-scavenging ability and extracellular polysaccharide production of the strain were determined, and then the in vitro safety test was performed to evaluate the safety of the strain to mice. The results showed that the strain P2M1 was Lactobacillus reuteri. It had the glycolysis ability, the logarithmic growth phase was 2~10 h, and the pH was stable between 4.0 and 4.1 after 20 h. It has good low-pH and bile salt tolerance, and is sensitive to common antibiotics. the DPPH, ABTS and hydroxyl radical-scavenging rates of the fermentation supernatant of the strain were significantly higher than those of the intact cell suspension (P<0.05), which were 88.79%, 93.52% and 92.15%, respectively. The yield of crude extracellular polysaccharide was 339.82 mg·L^-1. No death or organ lesions were observed in mice after intragastric administration of 0.2 mL of live Lactobacillus reuteri P2M1 solution at a concentration of 1×10⁹ CFU·mL^-1 per day for two weeks. It is concluded that Lactobacillus reuteri P2M1 has a short logarithmic growth period, rapid growth of cell concentration, high yield of extracellular polysaccharides, good probiotic and antioxidant properties, and safety in vitro, and can be used as a candidate strain for probiotic preparations.