The oxidizability of NO3 radical in the night is comparable with that of diurnal OH radical. Given the importance of NO3 radical in the nocturnal chemical process, accurate measurement of its concentration in the atmosphere has become an essential topic in current research. NO3 radical has the short lifetime and low concentration (approximately several hundred ppt), which brings a challenge to detect NO3 radical. In the 1980s and 1990s, differential optical absorption spectroscopy (DOAS) and matrix isolation electron spin resonance (MI-ESR) are mainly applied to detect NO3 radical. With the rapid development of technology, cavity ring-down spectroscopy (CRDS), cavity enhanced absorption spectroscopy (CEAS), laser induced fluorescence (LIF) and chemical ionization mass spectrometry (CIMS) are gradually developed to detect NO3 radical at the beginning of this century. The detection processes of NO3 radical are reviewed, the principles of several methods, the advantage and disadvantage of them are introduced in brief. In addition, the process of field observations are outlined.