Photodetector is an essential component in the effort to develop optoelectronic information system. Magnesium ferrite (MgFe2O4) with a band gap around 1.9 eV is expected to serve as a good photosensitive semiconductor for UV–Vis photodetectors. Here, the first MgFe2O4 microfibers based photodetector was demonstrated by combining the unique one-dimensional morphology of microfibers and the photoelectric conversion performance of MgFe2O4 semiconductor. The uniform MgFe2O4 microfibers were prepared by electrospinning method and then transferred to the FTO (fluorine-doped tin oxide) conductive substrate to obtain the simple photodetector. The device exhibited nearly linear response to 360 nm UV light with a maximum responsivity of 63.1 μA/W. It also showed a significant response to 450 nm blue light. Our findings not only provide a feasible path for constructing MgFe2O4 based photodetector but also open up a brand new application field of MgFe2O4 semiconductor.