Ce~(3+), Tb~(3+) doped orthorhombic phases of KLu_2F_7 microcrystals with hexagonal disk morphology were synthesized by a hydrothermal method. Enhanced emissions of Tb~(3+) were observed in the Ce~(3+)/Tb~(3+) co-doped KLu_2F_7 sample compared to the Tb~(3+) single-doped KLu_2F_7. The energy transfer efficiency from Ce~(3+) to Tb~(3+) was calculated by the photoluminescence intensity in the Ce~(3+)/Tb~(3+) co-doped KLu_2F_7 samples. The average separations between Ce~(3+) and Tb~(3+) were calculated and the critical distance was 0.922 nm estimated by method of concentration quenching. The theoretical calculation proved the results. The theoretical analysis also suggested that the energy transfer from Ce~(3+) to Tb~(3+) in the KLu_2F_7 occurred predominantly via the dipole-quadrupole interaction. The KLu_2F_7 should be good host materials for emitters. Ce (3+), Tb ~ (3+) doped orthorhombic phases of KLu_2F_7 microcrystals with hexagonal disk morphology were synthesized by a hydrothermal method. Enhanced emissions of Tb ~ (3+) were observed in the Ce ~ (3 +) / Tb ~ (3+) co-doped KLu_2F_7 sample compared to the Tb ~ (3+) single-doped KLu_2F_7. The energy transfer efficiency from Ce ~ (3+) to Tb ~ (3+) was calculated by the photoluminescence intensity in the average separation between Ce ~ (3+) and Tb ~ (3+) were calculated and the critical distance was 0.922 nm estimated by method of The theoretical analysis also suggests that the energy transfer from Ce ~ (3+) to Tb ~ (3+) in the KLu_2F_7 occurred predominantly via the dipole-quadrupole interaction. The KLu_2F_7 should be good host materials for emitters.