The absorption spectrum, upconversion fluorescence spectrum and infrared absorption spectrum of Er3+-doped bismuth-germanate glass, which was prepared by conventional high-temperature melting-annealing method with the heavy metal oxide composition of Bi2O3-GeO2-PbO, are investigated, and the research focus is on the upconversion fluorescence mechanisms of Er3+ under the 975 nm and 800 nm laser excitation. The results show that the green and red emission centered around 529 nm, 552 nm and 667 nm, corresponding to the 2H11/2→4I15/2、4S3/2→4I15/2 和4F9/2→4I15/2 transitions of Er3+, respectively, are simultaneously observed under the 975 nm and 800 nm laser excitation. A two-photon upconversion process is assigned to the green and red emission. Compared to the 800 nm laser excitation, a more intense upconversion fluorescence can be obtained under the 975 nm laser excitation, and the green emission intensity is greater than that of the red emission, which indicates that the bismuth-germanate glass is a more promising glass host material applied to the green upconversion.