A series of Eu3+ doped and Eu3+/Sm3+ co-doped borate glasses was successfully synthesized by melt quenching and annealing. Luminescence properties, concentration quenching and energy transfer were examined through fluorescence spectra and decay curves. Results showed that the main concentration quenching mechanism of Eu3+-single-doped samples was nonradiative energy transfer through exchange interaction between Eu3+. Eu2O3 at the optimized concentration of 8mol% was co-doped with Sm2O3 at various concentrations ranging from 0.3mol% to 2.0mol% to study energy transfer between Sm3+ and Eu3+. Results indicated the existence of energy transfer from Sm3+ to Eu3+ upon 403nm excitation. Fluorescence decays further revealed that energy transfer occurred between Eu3+ and Sm3+ in Eu3+, Sm3+ co-doped samples.