Single crystalline octahedral Zn doped Fe 3 O 4 was successfully prepared through a simple hydrothermal method without the assistance of any surfactant or template. Porosity and crystalline properties characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). Results showed as-synthesized Zn doped Fe 3 O 4 are uniform octahedrons with high crystalline. In addition, the possible mechanism for the formation of octahedral products via the time-dependent experiments and the role of hydrazine hydrate in the synthesis process was also discussed. Their photo-Fenton activity in photodegradation of Rhodamine B under visible light was sequentially investigated, indicating the high photocatalytic capacity of as-obtained octahedrons.