Abstract: The effect of chitosan on antibacterial stability of Nisin was investigated, and the protection mechanism of chitosan to the Nisin was also explored by infrared (IR) spectroscopy and differential scanning calorimetry (DSC) . The results showed that chitosan could significantly improve the antibacterial stability of Nisin. This effect had some discrepancies with different temperature and pH values. The antibacterial stability of Nisin was the best when the concentration of chitosan was 1%. The IR spectra and DSC thermogram showed that the form of hydrogen bonds between chitosan and Nisin could stabilize the structure of Nisin and improve its thermal stability, thus antibacterial stability of Nisin got better.