Doxycycline is a semi-synthetic tetracycline antibiotic obtained by deoxygenation of oxytetracycline at the 6α-position, and the preparation is hydrochloride. Its mechanism is the same as that of tetracycline, mainly interfering with the protein synthesis of sensitive bacteria. It can specifically bind to the 30S subunit of the bacterial ribosome at the A position, thereby inhibiting the binding of aminoyl-tRNA at this position and preventing the extension of peptide chains; Doxycycline can also change the permeability of bacterial cell membranes, causing nucleotides and other important components in the cell to leak out, thereby inhibiting the replication of bacterial DNA. Doxycycline has strong antibacterial activity against Staphylococcus aureus, Streptococcus pneumoniae, Streptococcus pyogenes, gonococcus, meningococcus, Escherichia coli, aerobacter, Shigella, Yersinia, Listeria core solo, etc., and also has certain effects on rickettsia, mycoplasma,