Lattice vibrations of barium metaborate (β-BaB2O4) crystal are analysed with the aid of group theory. The β-BaB2O4 crystal belongs to space group C34 (R3) with its vibration modes classified by the site-symmetry method . The result is, Γ=126A + 126E. All of these modes are both Kaman active and infrared active. The Raman, spectra of β-BaB2O4 are observed in different geometric configurations for the first time. Using a model called layer-molecular structure , the experimental results can be explained stisfaotorily with a preliminary assignment of the internal and external modes of β-BaBaO4 crystal.