DNA-CTMA complexes were prepared by ion-change method and DNA-CTMA thin films were fabricated by self-assembled and spin-coating methods. The photo-electrical properties of DNA-CTMA thin films were characterized by the measurement of the absorption spectra in the UV/vis/inf and far-infrared, refractive index and Alternating Current (AC) resistivity. The experiment results show that the transmissivity of the DNA-CTMA thin films is high in the telecommunication wavelengths, and there is a strong absorption only in the ultraviolet range of 230~315 nm and the infrared range of 2.7~3.34 μm, including two strong absorption peaks at 3 418 nm and 3 504 nm in the absorption spectra. Furthermore, in the preparation process of the films, the some factors of influencing the refractive index of film were analyzed, such as the butanol remained in film, temperature and the dry time. And the AC resistivity of 50 bp short DNA-CTMA thin film is less 2~3 orders of magnitude than the 2 000 bp longer DNA-CTMA thin film.