A series of biochar (BC) supported cadmium sulfide (CdS) composites (BC@CdS) were prepared by in-situ hydrothermal growth strategy using biomass gasification char residue as raw material. The structure and physicochemical properties of the composites were characterized by XRD, SEM, BET, XPS, UV-Vis DRS, PL, and EIS. Taking levofloxacin (LVF) as the target pollutant, the effects of different m(BC)∶m(CdS) on the BC@CdS photocatalytic performance were investigated, and then the effects of the dosage of BC@CdS for the optimal photocatalytic performance, the initial mass concentration of LVF, the pH value of the system environment, co-existing ions and humic acid (HA) on the degradation rate of LVF were investigated, and the cyclic stability of material and its applicability to different pollutants were also investigated. Finally, the mechanism of BC@CdS photocatalytic degradation of LVF was speculated. The results showed that the CdS nanoparticles grew uniformly on the surface of BC, which effectively prevented their own agglomeration. BC@CdS-2 prepared with m(BC)∶m(CdS) = 1∶2 had the best photocatalytic performance which showed that the degradation of LVF (50 mL) with a mass concentration of 20 mg/L could rached to 90.87% by 20 mg BC@CdS-2, and degradation rate of LVF was 85.45% after recycled for 5 times under visible light irradiation for 90min. The degradation rates of different pollutants (ciprofloxacin, ofloxacin, oxytetracycline hydrochloride, romindane B) with mass concentration of 20 mg/L were 83.57%~93.65% by BC@CdS-2. It had anti-interference ability to the pH value of the system environment and co-existing ions. Hole (h+) and superoxide radical (?O– 2) were the main active groups in BC@CdS photocatalytic system. The reason for the enhanced photocatalytic activity of BC@CdS was that the electron transport channel constructed by BC as a carrier increased the photogenerated electron transfer rate and enhanced the visible light response of the composite. At the same time, as the acceptor of photogenerated electrons, it promoted the photogenerated electron-hole separation of CdS body. The synergistic effect of the two improved the photocatalytic activity and cycle stability of CdS.