Abstract: Electronic structures and optical properties of ZnO, Bi-ZnO and 2Bi-ZnO are investigated with first-principles of plane wave ultra-soft pseudo-potential method based on density functional theory. It shows that variation trends of band gap of ZnO doped with different number of Bi atoms are not consistent. After doping, imaginary part of dielectric function peaks are broaden, and exhibit a red shift in the direction of low energy. Absorption peak, reflection peak and energy loss in high energy region decrease gradually as dopant atoms increased, which enhances transmission. Besides, absorption coefficient and reflection coefficient in visible and ultraviolet increase, which promotes the use of ZnO materials in visible light.