Orthorhombic phase α-BiNbO4∶Eu3+ and triclinic phase β-BiNbO4∶Eu3+ were synthesized by solid-state reaction method. Their structure and fluorescence properties were studied by X-ray diffractometer (XRD), Raman spectra, absorption spectra and luminescence spectra. Results indicate that pure α-BiNbO4 were successfully synthesized at 900 ℃, while triclinic phase β-BiNbO4 obtained at 1 200 ℃. The band structure of both structure BiNbO4 was studied using the first principle theory and absorption spectra. The optical band gap obtained for α-BiNbO4 and β-BiNbO4 are 2.69 eV and 2.96 eV respectively, in agreement with the theoretical result of 2.640 eV and 3.032 eV. After Eu3+ doping, theirs band gap blue shifts to 2.89 eV and 3.05 eV respectively, which effectively change their optical response range. The main emission peaks are from 5D0→7F2 transition of Eu3+ for both structural BiNbO4∶Eu, centerted at 615 nm and 611 nm respectively. But the emission intensity of β-BiNbO4∶Eu sample is much higher, and its luminescence intensity ratio between 5D0→7F2 and 5D0→7F1 transitions is much higher. For Er3+ doping, upconversion emission is observed for both structures excited at 980 nm. The upconversion emission intensity of β-BiNbO4∶Er sample is almost 40 times higher than that of α-BiNbO4∶Er sample. This results indicate that β-BiNbO4 is more suitable as the host material of rare earth ions doping phosphor.