The preparation of Tm:BaY₂F₈powders and the up-conversion luminescence of Tm:BaY₂F₈are reported in this paper. Excited by red light of 650 nm, two violet luminescence with peaks at 417 and 430 nm and the blue luminescence with peaks at 458 and 470 nm were observed. According to the spectral data reported here, the energy level scheme of Tm:BaY₂F₈was given, and the mechanism of the up-conversion luminescence was suggested.