The glass forming region of Bi_2O_3-B_2O_3-BaO ternary system was investigated.A serial of glass samples with high Bi2O3 content in Bi_2O_3-B_2O_3-BaO system were prepared by using conventional melting and quenching meld,and the refractive indexes and absorption spectra of samples were measured.It is found that the refractive index of samples as well as the UV absorption increase with the increase of BaO content.According to the Tauc law,optical band gap E_(opg) which is assumed to be the effective energy band gap Eg is calculated and decreases with the increasing BaO content,and the ratio of E_g/E_(opg) is 1.3.