Nd3+, Er3+ single-doped and Nd3+/Er3+ codoped tellurite glasses were prepared via a melt-quenching technique, and their optical transition properties were studied in the framework of Judd-Ofelt theory. The differential excited state absorption cross section from 4I(13/2) to 4I(11/2) was obtained based on the McCumber theory; furthermore, the optical gain coefficient spectrum for 4I(11/2)-> 4I(13/2) transition was calculated. The energy transfers 4F(3/2)(Nd3+)+4I(15/2) (Er3+)-> 4I(9/2)(Nd3+)+4I(9/2)(Er3+) and 4I(13/2)(Er3+)+4I(9/2)(Nd3+)-> 4I(15/2)(Er3+)+4I(15/2)(Nd3+) in the codoped sample were analyzed by using Foster-Dexter theory and Inokuti-Hirayama's model, respectively; meanwhile, the energy transfer rates for both the energy transfer processes were confirmed. The results indicated that Nd3+ may be a good sensitizer for Er3+ to obtain intense mid-infrared emission, and that Nd3+/Er3+ codoped tellurite glass may be a good candidate media for mid-infrared lasers.