We demonstrate the preparation and characterization of DNA optical nanofibers. The prepared DNA optical nanofibers with strong strength and high flexibility are tested. Coupled with silica fiber tapers, their optical characteristics including light transmission performance, group delay and chromatic dispersion are experimentally investigated. The visible and near infrared light waveguiding properties of the DNA optical nanofibers with and without R6G doping are also studied. It is expected that the DNA optical nanofibers may be potential for building the miniaturized biomedical photonic devices.