CuO/BiOCl-based electrode made AFB1 efficiently photoelectrocatalytic degraded. Display omitted •CuO/BiOCl composites were gained by in-situ growth of CuO on BiOCl surface.•The heterostructured CuO/BiOCl displayed greatly enhanced PEC response.•A CuO/BiOCl-based PEC biosensor was constructed for ultrasensitive AFB1 detection. Aflatoxin B1 (AFB1) exposure often causes serious food safety problems and illnesses in humans and animals even at extremely low content. Therefore, ultrasensitive detection and effective degradation of AFB1 is vitally significant. Photoelectrochemical (PEC) approach has been widely applied in sensing and catalysis fields. For achieving robust PEC performance, exploring highly photoactive semiconductor materials is critical. Herein, we constructed a novel and dual-functional copper oxide/bismuth oxychloride (CuO/BiOCl) composite by in-situ growth of CuO on BiOCl surface. The photo-absorption region of CuO/BiOCl was efficaciously broadened from UV to visible range, making for enhanced light harvest. Meanwhile, the p-n heterostructure in CuO/BiOCl clarified that the formed built-in internal electric field could accelerate band-band transfer of carriers. Driven by this, PEC response of CuO/BiOCl was greatly boosted comparing with that of pure CuO or BiOCl. Further combing with the specific aptamer, a favorable CuO/BiOCl-based PEC biosensor was fabricated for AFB1 detection with ultra-sensitivity (detection limit of 0.07 pg mL−1) and satisfactory recoveries (96.4% ∼ 105.7%) in real maize samples. Subsequently, under light irradiation and suitable bias voltage, a degradation rate of ∼81.3% was facilely attained for 5.0 µg mL−1 AFB1, indicating excellent photoelectrocatalytic activity of CuO/BiOCl material. The catalytic mechanism and the main product of AFB1 degradation were analyzed. Taken together, the heterostructured CuO/BiOCl-based PEC assay provides a potential way for monitoring and controlling the AFB1 contamination in the food security areas.