FT-Raman and surface enhanced Raman spectra (SERS) of norfloxacin and norfloxacin capsule on the silver colloidal substrate were recorded, and the vibrational and enhanced peaks were assigned; interactions of norfloxacin and DNA were researched. The experimental results proved that the characteristic vibrations of capsule’s content and NFX standard, which is ν(C—F), νs（O—C—O）, ν(CC), did not change, while the changes in molecular skeleton’s vibrations were substantial. Additives do not affect the Raman spectroscopy of norfloxacin substantively. An analytical method for detecting norfloxacin medcine can be established by FT-Raman. Without any ions,the interaction is mainly caused by the inserting-action mode between the ring of norfloxacin and the double helix structure of DNA, and norfloxacin could interact with DNA directly, providing reliable evidence for antibacterial mechanism of quinoxalone antibiotics.