Tb3+, Yb3+ codoped Y2O3 (mole fraction x=0.02, 0.05, 0.1) transparent ceramics of high transparency have been prepared by vacuum sintering and the down-conversion near infrared (NIR) emission has been demonstrated upon a 484 nm excitation. The dominant energy transfer mechanism is the cooperative down-conversion from 5D4 level of one Tb3+ ion to the 2F5/2 level of two Yb3+ ions. The suppression of Tb4+ during vacuum sintering and the suppression of Yb2+ due to the nature of Y2O3 lattice, together with the large energy gap between Tb3+5D4 level and Tb4+-Yb2+ charge transfer state (CTS) and the low phonon energy of Y2O3 make the non-radiative influence from the CTS negligible. In addition, the contribution of Tb3+5D4→one Yb3+2F5/2 (non-radiative)→Yb3+2F7/2 (radiative) process to NIR emission should be little due to the large energy gap between Tb3+5D4 level and low phonon energy of Y2O3.