TiO2, a kind of inorganic metal oxide semiconductor material, has been widely utilized. It is becoming a research hotspot to improve photocatalytic activity and photoelectric conversion property of TiO2 through incorporation of impurities. The electronic structure and optical properties of N doped, Cu doped and N- Cu co- doped rutile TiO2 are studied by using plane wave pseudopotential method of first- principles based on density functional theory. The results show that with N and Cu co- doped TiO2, new impurity energy levels would be formed in band gap of TiO2 due to the synergistic effect of 2p electrons of N and 3d electrons of Cu. Among them, one of impurity levels is in steady- state, the another level is in metastable state. It is favorable for decreasing the transition energy of electron and effective separation of photoproduced electrons- hole pairs, which largely improve the photocatalytic activity of TiO2. The curve of optical absorption coefficient of N-Cu co-doped TiO2 has larger red shift in the visible region than that of N doped TiO2 and Cu doped TiO2, and the reflectivity of N-Cu co-doped TiO2 also increases.