The absorption spectra, infrared (IR) absorption spectra and upconversion fluorescence spectra of a series of Er3+/Yb3+-codoped 46Bi2O3-44GeO2-10Na2O (B46G44N10) glasses were investigated, and upconversion luminescence mechanisms of Yb3+ sensitize Er3+ were analyzed. Upconversion fluorescence intensities of Yb3+ sensitize Er3+ were measured, the optimal doping ratio of Er3+ and Yb3+ was 1∶6 for this glass, which resulted in the strongest upconversion fluorescence intensities. An upconversion efficiency of 2.27×10-4 was calculated for green emission from the B46G44N10 glass with 0.5 wt.-% Er2O3, and 3.0 wt.-% Yb2O3 pumped by 980 nm. Results indicated that this kind of bismuth glasses might be potential materials for developing upconversion optical devices.