The high recombination rate of Bi 12 O 17 Cl 2 carrier and the limitation of visible light absorption of TiO 2 seriously hinder the application of photocatalytic water treatment pollution. In this work, we grow Fe 2 O 3 and Fe 2 TiO 5 uniformly in situ on TiO 2 –Bi 12 O 17 Cl 2 (hydrothermally constructed) heterojunction nanomaterials by the ion exchange method. Thus constructing a kind of three-heterojunction composite photocatalyst. XRD, SEM, XPS and other characterization tests were performed on the product to show the sample's morphology, composition, and photoelectric properties. The prepared photocatalyst induces photoelectrons under visible light and shows excellent photodegradation mineralization properties for methylene blue. Besides, the catalyst has cycle practicability and stability. Finally, through the valence band theory and the active species capture experiment, the degradation mechanism of the heterojunction's synergistic effect and the Fenton effect is proposed. The construction of nanocomposite provides a promising photocatalytic strategy for the Fenton reaction system based on heterojunction. • Prepared new photocatalyst Bi 12 O 17 Cl 2 –TiO 2 NW/Fe 2 TiO 5 /Fe 2 O 3 by Hydrothermal method. • The degradation rate of methylene blue reached 99.0% at 60min. • The degradation rate was 25.9 times that of adding photocatalyst alone. • The degradation efficiency is 11.2 times that of adding H 2 O 2 alone. • Heterojunction and Fenton effect synergistically improve photocatalytic performance.