Based on density functional theory calculations, the stability, the electronic structure and optical properties of La and Nb doped BaSnO3 were investigated. The calculated results reveal that due to the electron doping, the Fermi level shifts into conduction bands and the system shows n-type degenerate semiconductor features. At the same time, the density of states (DOS) of the two systems shift towards low energies and the optical band gaps are broadened. The optical transmittance is higher than 80% in the visible range for La and Nb doped BaSnO3 systems.