The Tm 3+ /Er 3+ :NaGd(MoO 4 ) 2 crystal with dimensions of Φ22×30mm 3 was grown by Czochralski method. Polarized spectra and fluorescence lifetime for the 4 I 13/2 (Er 3+ )→ 4 I 15/2 (Er 3+ ) transition at room temperature were investigated. Based on the Judd–Ofelt theory, the spontaneous transition probabilities, the fluorescent branching ratios and the radiative lifetimes were calculated. The fluorescence lifetime was measured to be 1.81ms. The detailed excited-transition mechanism with 800nm radiation is also discussed.