The theoretical calculation on benzotriazole(BTA) and its different substituent derivatives has been carried out by using density functional theory (DFT). The effect of different substituents on the geometric configuration and electronic structure of BTA molecule is discussed. On the basis, the lowest singlet excited states have been obtained by configuration interaction singles(CIS) method, and the properties of electronic spectra have also been investigated by busing time-dependent DFT(TD-DFT). The results show that, during the transition from ground state to excited state of benzotriazole and its different substituent derivatives, the geometrical structure changes are mainly focused on the bond length of benzene ring and conjugated heterocycle, and the major transition contribution is resulted from HOMO to LUMO transition, mainly π→π^* transition. The introduction of different substituents to the BTA molecule causes a bathochromic shift for both absorption and emission spectra.