Abstract: The discharge of antibiotic drugs in soil and natural water bodies can endanger the survival of algae and lower organisms, and may bring continuous damage to the ecological environment. For this reason, in this study, magnetic coconut shell biochar (MBC) was prepared by impregnation, co-precipitation and hydrothermal synthesis using tetracycline (TC), a local speciality agricultural waste in Zhanjiang, as raw material, and FeCl₃ and FeSO₄ as iron sources. The surface morphology and chemical structure of the samples were characterised using SEM, FTIR, XRD, BET, VSM and XPS. The effects of contact time, initial TC concentration, pH, reaction temperature and different concentrations of metal ions on the adsorption of TC by MBC were investigated. The results showed that MBC had the best adsorption effect on TC at pH 4.0 and reached adsorption saturation at 24 h. The saturated adsorption amount was 36.40 mg·g⁻¹, and the TC removal rate reached 93.37%. High concentrations of Ca²⁺ and Mg²⁺ significantly reduced the adsorption of TC by MBC, while the effect of Na⁺ was small. The adsorption kinetics conformed to the proposed secondary kinetic model, and the isothermal adsorption behaviour conformed to the Langmuir model, with the maximum adsorption capacity up to 46.49 mg·g⁻¹ at 45℃. The increase in temperature contributed to the increase in the adsorption capacity, which indicated that the adsorption process was a heat-absorption reaction. The adsorption mechanism mainly involves π-π interactions, hydrogen bonding and ligand bonding formation. The MBC showed excellent stability in the reusability experiments, and the removal rate remained stable at 85.16% after five adsorption-desorption cycles. It is shown that magnetic coconut shell biochar is an efficient and reusable TC adsorbent material, which has a good application prospect in the fields of breeding tail water and pharmaceutical wastewater treatment.