Abstract: The rapid growth of drug-resistant bacteria and the lack of availability of new treatment strategies make it urgent for people to develop new bacteriostatic agents to solve such problems. In this study, copper nitrate trihydrate Cu(NO₃)₂·3H₂O was used as a raw material and hydrazine hydrate as a reducing agent to prepare cuprous oxide (Cu₂O/CuO), then Cu₂O/CuO-tetracycline composites were obtained by combining them with tetracycline. Systematic characterization of inhibitors was conducted using TEM, XRD, XPS, FTIR, and UV-vis. The inhibitory properties and mechanism of Cu₂O/CuO-tetracycline on the Gram-positive bacterium Staphylococcus aureus (S. aureus), Gram-negative bacterium Escherichia coli (E. coli), and drug-resistant bacterium Salmonella (T-Salmonella) were studied. The results of antibacterial properties show that the antibacterial rate of Cu₂O/CuO-tetracycline composites with antibacterial concentration of 150 µg/mL to E. coli, S. aureus, and T-Salmonella reached 99.99% at 80 min. Compared with tetracycline and Cu₂O/CuO alone, the antibacterial efficiency of Cu₂O/CuO-tetracycline composite increase by 2.50 and 1.38 times for E. coli, 1.58 and 1.18 times for S. aureus and 1.26 and 1.12 times for T-Salmonella, respectively. In a word, Cu₂O/CuO-tetracycline composites are the most sensitive to E. coli. The antibacterial mechanism shows that the composite material can effectively destroy the bacterial cell wall, change the membrane permeability, and finally make the bacteria rupture and die. The Cu₂O/CuO-tetracycline composites have excellent antibacterial properties, indicating their wide application prospects in the fields of medical devices and medical materials.