The invention discloses an application of a 2-aryl-9-aryl-6,7-dihydro-3H-[1,2,4]triazine[1,3]thiazepine-3-ketone derivative represented by the general formula I shown in the specification to antibacterial drugs. R1 and R2 are hydrogen, a methoxy group, a nitro group, a methyl group, halogen, a hydroxyl group, an acetyl group, a propionyl group, a benzoyl group, an alkoxy group, an amino alcoxy group and a carbamyl alkoxy group independently. The compound has an obvious inhibition effect on various bacteria such as MRSA (methicillin-resistant staphylococcus aureus), Escherichia coli, pseudomonas aeruginosa and the like and can be applied to preparation of the antibacterial drugs.