Abstract: (Y,Gd)BO₃:Eu³⁺（YGB:Eu³⁺） red phosphor was synthesized by the coprecipita-tion method.The XRD result shows that crystal parameters of YGB:Eu³⁺ increase and the crystal lattice distortion occurs to some extent while the concentration of Gd³⁺ increasing.The luminescent efficiency of YGB:Eu³⁺ under VUV is relative to the matrix absorption and CTS of Eu³⁺-O_2-,and the former is the major factor.The red-shift of absorption bands of the matrix and CTS exists with addition of Gd³⁺ in YGB:Eu³⁺.Gd³⁺→Eu³⁺ energy transition exists under UV radiation.The concentration of Gd³⁺ is of no importance to the position of emission peaks of YGB:Eu³⁺ due to the shield of Eu³⁺ 5s5p orbits.The color purity of YGB:Eu³⁺ improves with the increase of concentration of Gd³⁺,because of the increase of the number of Eu³⁺ which occupy the symmetry centers in the crystal cell resulting from the change of crystal field.Suitable crystal distortion is helpful to the luminescent efficiency of YGB:Eu³⁺ under VUV,and the optimum concentration of Gd³⁺ is 0.3 mol.