The Tm3+ single-doped and Tm3+/Ho3+ co-doped tellurite glasses are prepared by traditional melt quenching technique. The synthesized glasses were characterized with infrared and up-conversion fluorescence spectra has been investigated in terms of the excitation of 808 nm laser, and the up-conversion fluorescence composed of four emission bands centering around 695, 544, 474 and 740 nm wavelengths, respectively. The 740 nm emission band seldom reported is possibly assigned to the Tm3+: 1D2→3F2, 3 transition by analyzing the spectra properties of the glass samples and relevant energy transfer mechanism. The intensities of 740, 695 and 474 nm emission in the tellurite glass at the concentration of 0.5 mol% of Tm2O3 and 0.3 mol% of Ho2O3 are almost 3, 2.5 and 14 times larger than those in the tellurite glass at the concentration of 0.5 mol% of Tm2O3, respectively. These obviously indicate that there is backward energy transfer from Ho3+ to Tm3+. The population for the energy level 1D2 (emitting 740 nm red) of Tm3+ in Tm3+ single-doped tellurite glass is significantly originated from cooperative up-conversion (CU). However, the population for the energy level 3F2, 3 (emitting 695 nm red) of Tm3+ is not only resulted from the process of CU, but also from the 1D2→3F2, 3 transition and the relaxation of the level 1G4 of Tm3+. Hence, the intensity of 695 nm emission is evidently higher than that of 740 nm emission in the samples. Because of the cross relaxation CR2 and CR3, as well as backward resonant energy transfer RET2, there is a net increase of population for the level 1G4 (emitting 474 nm blue) of Tm3+ in the Tm3+/Ho3+ co-doped tellurite glass compared to the Tm3+ single-doped tellurite glass while the two glasses are conformed with the concentration of Tm3+. The net increase of population for the level 1G4 of Tm3+ is possible to reinforce the multi-phonon relaxation process of this level, emission of 740 nm red light, as well as CU process, and further enhance the population for the level 3F2, 3 of Tm3+. Therefore, the intensities of red and blue fluorescence in the Tm3+/Ho3+ co-doped tellurite glass are clearly greater than those in the Tm3+ single-doped tellurite glass. The effects of cross relaxation and energy transfer between Tm3+ and Ho3+ are studied, while the energy transfer mechanism between Tm3+ and Ho3+ is also further discussed in the work.