The electronic structures and optical properties of Tb1-xYbxMnO3 as a function of Yb element content x are investigated by employing the first-principles method.The calculation results indicate that the electronic states associated with the Yb element are dominated gradually and the inner electronic states move to the lower energy level with the increasing x.The dielectric function and other optical properties of Tb1-x YbxMnO3 such as the reflectance spectra are obtained and the results indicate that the static dielectric function reaches a maximum at about x =0.75,while the fitting expression predicts a maximum when x =0.69.In addition,it is found that one peak appearing at about 3.60eV in the reflectance spectra of TbMnO3 is driven to shift linearly towards higher energy level with the increasing x.However,another peak at about 29.63eV moves nonlinearly in the same situation.