Aflatoxin B1 (AFB1) is a carcinogenic toxin naturally produced in most food crops that severely threaten human health, and effective methods are urgent to improve the detection accuracy. Herein an indirect competitive immunosorbent approach was elaborately developed based on high-affinity immunoglobulin G (IgG) coupled CuO-anchored Fe3O4 nanozymes for precise and ultrasensitive detection of AFB1 in food crops including peanut, corn and wheat. The high-affinity nanozymes were fabricated by the assembly of inner core Fe3O4 nanoparticles and mesoporous silica capping layer, CuO further situated within large aperture of the coating layer via in-situ growth, and then conjugated with ligand rabbit anti-mouse IgG, which can specifically bind with AFB1. The results showed the hybrid high-affinity nanozymes displayed enhanced peroxidase-mimic activities and catalytic performances, achieving a linear range of 0.06−61.93 (lg(ng/mL)) and a detection limit of 0.003 7 ng/mL, 30 times better than that of the conventional enzyme-linked immunosorbent assay. The constructed nanozymes were successfully applied to the detection of AFB1 in food products with an average spiked recovery of 96.53% and relative standard deviations less than 2.8%. Therefore, the accurate hybrid nanozymes may serve for AFB1 detection in various foods in future.