In this paper, the energy band structure and properties of Nb doped ZnO with different concentration were calculated based on the first-principle of density functional theory, and the simulation results of intrinsic ZnO, Al doped ZnO (AZO) and Nb doped ZnO (NZO) were compared and analyzed. The results show that: (1) the band gap values of NZO and AZO are lower than that of intrinsic ZnO, and the band gap values of NZO with the same concentration of 6.25% are lower than that of AZO. With the increase of Nb doping concentration, the conduction band bottom and the peak density of states of NZO decrease obviously, and Nb-4d electrons occupy the main quantum states of Fermi level. (2) With the increase of doping concentration, the absorption peaks and dielectric function peaks of NZO and AZO decrease, and move to the low energy region. Among them, the absorption peaks of NZO move more obviously to the low energy region, and the imaginary part of dielectric function has new peaks at 0.42 eV and 34.29 eV respectively, which is mainly due to the transition of Nb-4d and Nb-5p electronic energy levels in the valence band. The static dielectric constant of NZO with the same concentration of 6.25% is greater than that of AZO, which indicates that NZO has stronger polarization ability, and NZO can improve the photoelectric properties of ZnO more effectively. With the increase of Nb doping concentration, the absorption coefficient and the imaginary part strength of dielectric function of NZO increase and move to the high energy region. The theoretical simulation results of NZO provide a theoretical reference for the experimental research and practical application of high valence element Nb doped ZnO.