Abstract: In order to efficiently adsorb enrofloxacin (EFA) in water, coconut shell biochar (BM-KOH-BC) was prepared by modifying coconut shell through ball milling and KOH activation, and in-depth research was conducted on the adsorption of EFA. BM-KOH-BC was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. The results revealed that KOH activation and ball milling modification significantly improved the pore structure and specific surface area of BM-KOH-BC. Under optimized conditions (Initial EFA concentration is 80 mg·L⁻¹, pH value is 7, temperature is 25℃, adsorbent dosage is 0.14 g·mg·L⁻¹, stirring speed is 200 r/min, contact time under the conditions of 35 h), BM-KOH-BC showed good adsorption performance, with a removal rate of 77.4% and a maximum adsorption capacity of 481.1 mg·g⁻¹. The adsorption process is consistent with the second-order kinetic model and Freundlich isotherm model. In addition, BM-KOH-BC still maintains efficient EFA removal rate after 5 adsorption-desorption cycles. This low-cost, efficient adsorption and recyclability feature makes BM-KOH-BC show potential application prospects in treating EFA in water bodies.