The samples of Er3+-doped, Yb3+∶Er3+co-doped borosilicate glasses with different dopant concentrations were prepared by the high-temperature sintering technique.Based on Judd-Ofelt (J-O) theory, the J-O intensity parameters Ωk(k=2,4,6), spontaneous radiative lifetime, spontaneous transition probability, fluorescence branching ratio, and spectral line strength of the Er3+ ions were calculated. While the stimulated emission cross sections of the up-conversion red (4F9/2→4I15/2) and green (2H11/2→4I15/2) emission of Er3+ions were analyzed using McCumber theory. The results show that J-O intensity parameter Ω2 becomes smaller with the increase of erbium concentration in Er3+-doped borosilicate glasses. But for the Yb3+∶Er3+ co-doped borosilicate glasses, the value of Ω2 becomes bigger with the increase of ytterbium concentration, and bigger than that of silicate, fluorid, and bismuth glasses reported. The stimulated emission cross sections of the up-conversion red and green emission increas a little.