This study investigated the synthesis and luminescence properties of MgNb 2O 6 nanocrystals by citric gel process. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy, high-resolution transmission electron microscopy, and photoluminescence (PL). The PL spectra excited at 270 nm had a broad and strong blue emission band maximum at 450 nm, corresponding to the self-activated luminescence of the niobate octahedra group [NbO 6] 7−. The optical absorption spectra of the 800 °C sample exhibited the band-gap energy of 3.6 eV. Furthermore, the microstructure and luminescence spectra of the products were investigated.