New noncentrosymmetric double borate Rb3EuB6O12 was synthesized by solid state reaction method, and their crystallographic parameters were obtained by Rietveld analysis. This borate crystallizes in the trigonal space group R32 with cell parameters of a = 13.4604(2) Å, c = 30.7981(5) Å, Z = 15. Their structure features a three-dimensional framework composed of [B5O10] 5groups that are bridged by Eu-O polyhedra. The existence of B5O10 group in the structure was confirmed by vibrational spectroscopy. Rb3EuB6O12 melts incongruently at 1101 K. The second harmonic generation effect of Rb3EuB6O12 is 16 times higher than that of α-quartz standard. In the luminescence spectrum, the domination of a single prominent narrow line from hypersensitive 5 D0-7 F2 manifold of Eu 3+ ions is observed, while 5 D0-7 F1 manifold and ultranarrow 5 D0-7 F0 line are of comparable peak intensity. These features are explained by specific local symmetry of Eu ion within the crystal structure of Rb3EuB6O12..