A series of LiSr1-xPbxBO3(x = 0.138,0.285,0.320,0.379,0.417,0.5)crystals have been obtained by a high-temperature solution reaction with spontaneous nucleation technique,and the crystal structures were solved from single-crystal X-ray diffraction.Through a great deal of experiments,the maximum value of x cannot be greater than 0.5 possibly because the continuously increased Sr/Pb-O bond length and the equivalent isotropic displacement parameter of O(3)atoms with the increased ratio of Pb2+cations.It is found that when the Sr atoms partially substituted by Pb atoms with optical anisotropies,the birefringence improved from 0.0494@1064nm in LiSrBO3 to 0.0721@1064nm in LiSr0.5Pb0.5BO3.Basing on the first-principles and real-space atom-cutting method,the origin of birefringence was attributed to the Pb2+cations and(BO3)3-groups in LiSr0.5Pb0.5BO3.The infrared spectrum properties and thermal behavior were also reported.