The Raman, absorption, luminescence spectra and lifetimes curves of Sm3+-doped K2GdF5were measured. Based on the Judd-Ofelt analysis, the values of radiative transition probabilities, branching ratios, integrated emission cross-sections and radiative lifetimes of excited states of Sm3+ in K2GdF5 crystal were calculated. The migration of excitation energy between the Gd3+ ions and the trapping processes of Gd3+ excitation energy by Sm3+ and Tb3+ions in K2GdF5 crystal are reported. The role of the overlapping between the broad, allowed absorption bands of the RE3+ ions and the narrow absorption lines 6IJ and 6PJ of Gd3+ ions on the trapping rates of the RE3+ was discussed. The energy transfer between the Sm3+ ions was studied by the decay measurement, which has been fitted by Inokuti-Hirayama energy transfer model and revealed that electric dipole–quadrupole interaction is responsible for the energy transfer process in Sm3+ ions doped K2GdF5 crystal.