Magnesium ferrite (MgFe2O4) nanofibers were synthesized by direct annealing of electrospun precursor fibers using an appropriate heat treatment process. The crystal structure, morphology and surface area of the as-synthesized MgFe2O4 nanofibers were investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy, respectively. The optical properties of the as-synthesized products were studied through ultraviolet-visible and photoluminescence spectroscopy. Due to its potential application in photocatalysis, the photocatalytic degradation of tetracycline (TC) was conducted, and the result indicated that MgFe2O4 showed a better photocatalytic degradation ratio (1.5 times and 2 times) of TC than the others under visible-light irradiation, which may be due to the unique rod-in-tube structure, and Larger specific area and the Larger specific surface area could absorb more catalyst and provide more active sites.