Emission spectroscopy of the high-voltage pulsed positive corona discharge in a line-cylinder reactor is used to investigate the high-energy electron density distribution in the discharge gap. The relative overall emission intensity spatial distribution profile of the A 2 Σ + ->X 2 Π transition of NO is successfully recorded against a severe electromagnetic pulse interference coming from the corona discharge at one atmosphere. The spectroscopic investigation shows that the high-energy electron density in the discharge has a nonlinearly decline in the radial distribution. When varying the discharge voltage, the absolute emission intensity of NO is different but the radial distribution profile is similar. If an oxygen flow was introduced into the discharge reactor, the emission intensity of NO decreases tremendously and, therefore, the high-energy electron density decreases reasonably.