Abstract: Deoxynivalenol (DON), a common mycotoxin, is a harmful secondary metabolite produced by Fusarium graminis and other fungi infecting grains or feed, which poses a great threat to the economic value and safety of food and feed. The degradation methods of DON mainly include physical adsorption, chemical treatment and biodegradation, among which the physical treatment methods include grinding, heat treatment and ion emission. Traditional physical adsorption methods cannot convert toxins into non-toxic compounds, resulting in nutrient loss in food and feed. Chemical treatment can effectively destroy DON′s structure, but it also introduces other chemicals that can affect the quality of grain and feed. Microorganisms can reduce or remove the toxicity of DON under mild conditions, and have little impact on sensory properties and palatability of raw materials, which has become an effective method to degrade mycotoxins at present. In this study, a strain that uses DON as the only carbon source and degrades DON was screened from the intestinal tract of pigs, and it was identified as Bacillus velezensis by 16S rDNA sequence comparison. The results showed that the degradation rate of DON by Bacillus velezensis reached 76.7% after incubated at 37 ℃ for 72 h. In addition, the main active substances in the process of DON degradation by Bacillus velezensis were mainly derived from the cell-free supernatant. The degradation rate of DON decreased by 14.5 and 11.2 percent point in the supernatant treated by protease K and a high temperature, respectively, which may be due to the main role of extracellular proteins or enzymes in the degradation of DON. In addition, Bacillus velezensis could also inhibit Fusarium graminis. The growth of Fusarium graminis was inhibited in PDA medium, and the bacteriostatic rate reached 56.2%. Meanwhile, after centrifugation and filtration, the cell-free supernatant and liquid PDA medium were mixed and shaken, and Fusarium graminis inoculated on the mixed medium could also be inhibited. In detail, mycelial growth was decreased significantly, the germination of spores was inhibited, and the inhibition rate of fusarium graminis reached 63.2%. In this study, a strain of Bacillus velezensis with a high DON degradation rate of 76.7% was obtained through microbial screening. Through the study of the degradation mechanism of DON by Bacillus velezensis, it is speculated that the substances that exerted the degradation activity may be extracellular protein or extracellular enzyme. Meanwhile, it was found that the strain had biological antagonistic effect against fusarium graminis, and the inhibition rate was up to 56.2%. This study provides a theoretical basis and resources for biological control of DON and Fusarium graminis.