Aflatoxin B-1 (AFB(1)) is regarded as a main biological pollutant with high toxicity, carcinogenicity and teratogenicity, and the double bond (C8=C9) of its terminal furan ring is the key hypertoxic site. Although semiconductor photocatalysis has been proposed to be a potential way of reducing or inactivating the toxicity of AFB(1), the reaction mechanism of reactive oxygen species with the hypertoxic site has not been defined so far. Herein, a kind of all-solid-state Z-schematic composite was fabricated by depositing CdS on the surface of clew-like WO3, which can sharply reduce the toxicity of aflatoxin B-1 in aqueous solution under visible light irradiation according to the cytotoxicity test result. On the bases of high resolution mass spectrum (HRMS), radical trapping test and O-18 isotope-labeling studies, it can be concluded that the preferentially inactivating the C8=C9 site by the addition reaction of hydroxyl radical was the main pathway for the detoxification of aflatoxin B-1. Furthermore, density functional theory (DFT) calculations were applied to reveal the reaction mechanism and verify that the hydroxyl radicals were most likely to react with the C9 site, and then form AFB(1)-9-hydroxy. This work provides in-depth insights into the inactivation mechanism of hypertoxic site in AFB(1), and the design of efficient photocatalysts for alleviating the risk of toxic pollutants.