Photofenton technology is one of the effective means to treat organic wastewater. Developing photofenton catalysts with a higher catalytic efficiency is always a hotspot. A BiOI/MIL-100(Fe) nanocomposite with a visible-light response was synthesized by a facile hydrothermal-co-precipitation method. The as-synthesized BiOI/MIL-100(Fe) nanocomposite was characterized by X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, UV-vis diffuse reflectance spectroscopy and N2 adsorption-desorption analysis, respectively. The BiOI/MIL-100(Fe) nanocomposite exhibits a better photo-Fenton activity rather than pure BiOI and MIL-100(Fe) for tetracycline degradation under visible-light irradiation. In particular, the composite (BiOI/MIL-100(Fe)-2) has the maximum efficiency when a content of MIL-100(Fe) is 5.2% (in mass fraction). The formation of BiOI/MIL-100(Fe) heterojunctions between BiOI and MIL-100(Fe) is beneficial to the transfer and separation of charge carriers. The photogenerated electrons accelerate Fe2+/Fe3+ cycle and create the reductive reaction of H2O2. The enhanced performance of BiOI/MIL-100(Fe) nanocomposite is ascribed to a synergic effect for photocatalysis and Fenton reaction.