Nitrate radical plays (NO3) an important role in the nighttime atmosphere. By using direct moonlight as light source, a passive differential optical absorption spetroscopy (DOAS) system with automatic star-finder system and CCD spectrometer, is developed to measure the nighttime NO3 vertical column abundance of NO3. Water vapor cross section is calculated using a line-by-line approach with considering the dependence of cross section on the temperature and water vapor amounts. By using air mass factor(AMF), the vertical column density (VCD) of NO3 radical is converted from slant column density (SCD). The max value of SCD is under 1.7×1014 molecule/cm2. As the sun rises, the observed column abundance decreases rapidly.