Objective This study aims to assess the effects of Fusarium on the malting process and malt quality of barley, screen out the microorganism with inhibitory activity against Fusarium, and explore the potential of this microorganism for degrading deoxynivalenol (DON).Method The mycotoxin-producing strain was isolated from domestic Dan’er barley contaminated with pathogenic fungi, and the interaction between the pathogen and the host was studied. The germination rate, water sensitivity, and DON mass fraction were compared between the barley infected for 5 d and standard barley. The DON mass fraction, activities of protease, β-glucanase, and amylase, and physicochemical indicators (free amino acids, soluble nitrogen, and β-glucan mass concentration) of malt produced from infected barley were measured. The microorganism capable of inhibiting the viability of the mycotoxin-producing strain was screened from barley and malt. The effects of the freeze-dried cell-free supernatant powder (cfsP) of the microorganism on the growth and development of the mycotoxin-producing strain were studied, and the antifungal effects and mechanisms of cfsP at different mass fractions (0.020~0.100 μg/kg) were tested. During the steeping stage, the antifungal strain was inoculated and its regulatory effects on the DON mass concentration and the processing performance of malt were evaluated.Result The mycotoxin-producing strain was identified as Fusarium culmorum (F. culmorum). After being infected with this strain for 5 d, the barley showed a germination rate decrease of 45.8%, significantly increased water sensitivity, and the DON accumulation reaching 276 μg/kg. Compared with the control group, the malt produced from infected barley showed an increase of 6 times in DON mass fraction, a decreased activity of amylase, increased activities of total protease and β-glucanase, increased levels of free amino acids and soluble nitrogen, and a reduced mass concentration of β-glucan. Lactobacillus plantarum (L. plantarum) NM-6 capable of inhibiting F. culmorum was screened out. The L. plantarum NM-6 cfsP with a mass concentration ≥ 0.020 μg/kg changed the mycelial morphology of F. culmorum, and the cfsP with a mass concentration ≥ 0.050 μg/kg inhibited the growth of the germination tube of conidia. The cfsP with a mass concentration of 0.100 μg/kg completely blocked the growth of the strain, and its antifungal activity was stronger at low pH conditions. When 2×10? CFU/g of L. plantarum NM-6 was inoculated into barley during the steeping stage, the DON mass fraction in the malt was approximately 50% of that of the control malt, and the filtration and solubility properties of the malt were significantly improved.Conclusion The Fusarium species infecting Dan’er barley was identified as F. culmorum and the microorganism with inhibitory activity against F. culmorum was identified as L. plantarum NM-6. The infection of F. culmorum led to a decrease in the germination ability and accumulation of DON in barley. L. plantarum NM-6 can efficiently inhibit the spore germination and mycelial growth of F. culmorum by secreting acid-tolerant active substances. Its application in the malting process can simultaneously achieve toxin control and quality improvement, providing a biocontrol strategy for the safe application of barley exposed to fungal infections.