The combined pollution of heavy metals and organic matter in aquaculture water bodies threatens the quality of aquatic products and human health. In this study， aquatic plants from aquaculture ponds were used as raw materials to prepare biochar for adsorption and removal of heavy metal cadmium （Cd²⁺）， polycyclic aromatic hydrocarbons （PAHs） and enrofloxacin （EFX） in aquaculture wastewater. The adsorption effect was assessed by pollutant removal and risk （RQ） reduction， while the elemental composition， specific surface area， apparent morphology， physical phase structure and functional group composition were characterized by scanning electron microscopy （SEM-EDS）， X-ray diffractometry （XRD）， and Fourier Transform Infrared Spectrometry （FTIR）， respectively， and the preliminary adsorption mechanism was carried out in conjunction with adsorption kinetics and isotherm studies. The results showed that the specific surface area of BC500 was large， and C=C， C=O， -COO and -OH were the main functional groups of BC500.The average removal of Cd²⁺， FLU， PHE， FLT， PYR and EFX by BC500 ranged from 54% to 90%， and the RQ value of ecological risk was also reduced from 0.85 to 0.33， indicating the excellent removal performance of BC500 biochar. The results of adsorption kinetics and isothermal model simulation showed that the adsorption of BC500 biochar on the composite pollutants was dominated by the adsorption of chemical monomolecular layer， and there was a competitive adsorption between heavy metal Cd²⁺ and organic pollutants （PAHs and EFX）. In addition， the adsorption mechanisms of BC500 biochar on composite pollutants included oxygenated functional group complexation （Cd²⁺， PAHs， and EFX）， π-π interactions （Cd²⁺， PAHs， and EFX）， ion exchange （Cd²⁺ and EFX）， hydrogen bonding （PAHs and EFX）， and Cd²⁺-EFX complexation.