We have used optical emission spectroscopy to characterize the high-voltage pulsed discharge of ammonia. Am-monia was highly dissociated in the discharge at low pressures. More atomic nitrogen was generated as compared tothe discharge of nitrogen gas at the same pressure of 0.8kPa. We discuss the elimination of the oxygen impurity in theammonia discharge, and we estimate the time-dependent atomic excitation temperature and the electron density fromthe measured spectra.